Hey, someone took inspiration from my fortress!
For regular kota, you can have a 5x5 layout: the frame in the very centre, a 1-tile walkway around that, and a layer of wall/door on the outside.
For oversized kota buildings, think of it as very slowly painting your kota into existence from one side to the other. Plan out the trail your frame will go to build your kota and build the floors and walls around and behind (but not in front! frames can't go on floors) the frame, moving it one square away each time. You will always end up with one ground space when your kota is done.
For walls, you can go two ways about it. Contiguous walls (like in the old post) take more time, but are prettier. You'll build 3 wall sections every time you lay a frame. Don't build corner walls and move the frame just enough to continue the wall with another 3 walls. Repeat as needed.
If you don't care about aesthetics, you can build the corner walls and save time on assembling/disassembling the frame.
Whatever you do to get your oversized kota, there's one thing to remember: never build a wall next to a frame unless you want the frame to stay.
Edit: Pictures!
These are the standard kota layouts. You'll probably never see #3 in villages.
This is how to build a 7x7 kota (5x5 floor space). Lighter blue and yellow are where you will build walls and floors relative to where the frame (dark green) currently is; dark blue and yellow are previously-built walls and floors. The thin lines are the floor coverage of the framework.
This is how to build a kota wall: