Although I am not very enamoured of the idea of partially submerged sphere, toroids, ovoids etc for seasteading, I have to say I think that as a turn-key island-building solution, they may have some merit in places where the bottom is shallow enough.
I say turn-key meaning everything is built where there is access to building facilities, then it is floated to the location completely built. I imagine it being constructed so as to draft no more than 10'.
I think the Marinea Bahamas project area would be a good candidate for it. I can envision a toroid with rounded bottom being floated out into location, and set down in a controlled (reversible) scuttle. Housing can be built into the donut part of the toroid, with a beach built into the outer part of the ring (even if the beach is just concrete rather than accumulating sand.
The inner area would be a shallow, more or less conical area terraced into park/cropland, working space, and a freshwater reservoir in the middle. The freshwater reservoir could be supplemented with "underground" reservoir in the bottom of the toroid's outer ring which would be the ballast tanks for placing (and moving if necessary).
This freshwater ballast could always be pumped out to floating polymer bags without much loss if you needed to re-float and move the structure. These bags can be towed for some distance as freshwater floats on seawater. Even though the freshwater is slightly lighter than seawater, the additional mass of the toroid/tank walls would still make it heavier than seawater when filled.
Shape: The bottom could be smoothly rounded for leveling purposes, or could have a skirt built into it like many oil rig platforms do. This is a shallow water solution either way. It could have a smoothly rounded or ovoid outer perimeter, or it could include some extruded breakwater/bay areas, but these add points of engineering complexity and potential points of failure.
In the Bahamas reef area already under consideration, there are areas where the water is only 10-30' deep. That's not too bad for even a home scale build. A torus 50 feet in diameter (1962 ft^2) is the area of an average US home, almost 1/4 the size of an average suburban lot. Given an aspect ratio of 1/3 that would make it 16 ft high, or go with a 1/2 aspect ratio for 25 ft high. Sunk to 15' depth, that leaves 10' above the water, which is low but almost the average in the Bahamas. You can play with the aspect ratio per your own specific location and requirements. You shouldn't be able to get waves more than 7' high above average high tide in an area that is only 15' deep.
1962 ft^2 overall footprint with 1/2 aspect ratio: 25' high gives you two usable floors and sub-floor ballast tanks of 5'-7' in the bottom. Housing being up high in a ring around the outside still allows a good 10' of enclosed space all the way around the ring. About 648ft^2 in this top level (assuming 35' outer diameter, 20' inner diameter). Almost 3 times this much on the lower floor (pretty much the entire footprint at 1962 ft^2). So one room wide, along the length of the rim, and a 5' wide terrace (about 236 ft^2) on ground level for this floor on the inside of the ring. Conical pond that is about 10' in diameter by 10' , filled up to a couple feet below the inner terrace, holds nearly a thousand gallons. More if you make the sides steeper rather than conical. The pond can easily have a platform constructed over it for further workspace or greenery. Shading the pond keeps the water temps a little cooler and slows algal growth. The roof of the top row is yet more space for activities and items that don't need to be sheltered from wind.
Edit to add: Scratch the conical pond, just make it a cylinder. More than 12 tons in easily pump-able/removable ballast and 3 times as much freshwater storage as a cone. Easier to engineer and more stability, too. I was typing this up from a vague idea before I had enough coffee this morning. Also corrected some math for scaling.
The top floor could be designed mostly for group spaces, work spaces that have direct access to air and light on the inner and outer face, and the next floor down is wider and contains sleeping quarters.
You can always add breakwaters, play with the outer slope angles for more or less "beach-like" qualities. Building the housing into the outer, upper ring of the torus means you have a nice view/vantage for homes that feel open and inviting, while you put more of the systems, reservoirs, and machinery that maintain the place lower in the structure for both buoyancy/stability characteristics and because those are places to do work and the place to relax is up in the air and sun. The terraced inner slope (mimicking a volcanic island's caldera & lake) is also light and airy, but sheltered enough from winds to allow lots of activity and growing things. If the inner bit is open to the air, you can do freshwater aquaponics and aquaculture, and use to irrigate crops on higher terraces which trickle back down into your lake/pond, while freshwater reservoirs inside the shell are purified and sanitized to drinking water standards. You don't want to waste energy on doing that for irrigation water, but the larger volume of freshwater is an overall safety margin.
This structure would serve as a residential center point for further structures- breakwaters, floating real estate anchored or attached, floating docks for mooring alongside, etc. These things could pop up like mushroom in a fairy ring and BE the breakwater for other floating structures. The construction cost should be within sight of building a home on land, or a live-aboard vessel.