Better Chairs v1.0.0
Stand on a stair or a bottom slab block and position yourself so that you are in the block.
After positioning yourself correctly, right-click, and you should now be in a sitting position.
If you wish to sit at your current position regardless of the block you are on,
simply use /function main:force_sit
to seat yourself automatically.
Chairs will despawn if you move more than 5 blocks away from them.
Therefore, you must repeat the steps above to sit in different chairs.