Just did this recently. Here’s what mine looks like.
The reel is a GLI whirlwind. I’m still waiting on the metal base that should be on top of my posts, but they are backordered so the pics show my makeshift temporary solution.
The posts are 4x6 treated. Spaced 25 feet apart for my 24ft pool.
It works pretty well, except that the cover likes to pull toward the center of the pool when rolling it up. So I have to go from side to side periodically to pull it back out toward the outside. In total it takes 3 or 4 minutes to cover the pool and about 5 minutes to uncover it.