Tubes in space!
I heard about people planning to use the Starship body to as ad-hoc space stations, but I think that's missing the point.
SpaceX has demonstrated that with a roll of steel and a robotic welder you can make a tube.
Starship uses quite thick steel, a space station would probably be fine with 1mm steel.
Starship can launch 150 tons if I remember correctly.
So my space station plan is to have 3 tubes one inside the other. The outer tube is to protect against impacts, the 2 inner tubes would ideally be filled with water to protect against radiation.
Water from an asteroid, of course.
Connect these 3-tube sections with airlock sections, make into a ring, spin for effect.