Rough cut before surfacing
I’m with JimN on this one.
Rough cut the pieces to length before starting to square things up.
Assuming your legs are going to be say 22″ long, I would make a board that is 45″ long, flatten it on both sides, crosscut to 22.5″, rip all to the correct width. plane the remaining sides.
The final 0.5″ can be removed after assembly, when you make sure the saw bench touches the floor with all four legs.
I made a sawbench some years ago, and it is one of the most useful projects you can make in my opinion. I think I need to make another one at some point.