Cannot overemphasize the importance of sides being same length, and front back the same on just the drawer box, Only time that doesn't work is on a front for drawers with an overlap.
Just a drawer box front, front same, side side same.
Drawer with an overlay face. Face is wider, and taller than just the box. This is the only time front and back aren't exact same dimensions. Holding these together so they stay in the correct alignment would benefit from several hands holding while screwing, or using some clamps to hold position.
I don't make pocket hole drawers, but this piece had some interesting concepts you might want to read this over. He uses a clamp to hold the drawer square BEFORE he screws the screws in. This makes sense, based on my use of pocket holes I have found making parts mate tight against each other is pretty easy, and if your force is straight in, the join is pretty much made by the tightening screw. What I have found if the join is on an angle, or not straight in, the process of pushing the drill forward often moves the pieces, and this could surely cause even same size parts to move, and once joined, they could be out of square. I note in the pic I found of just the drawer box, the pieces are aligned like I am talking about. Same with the article. One thing you can do is on each corner put the front, or back down on the table flat, and then when you screw the side into the front or back, you are going straight down.
article is right here
Corner squares can be used if you use clamps to also hold the corner at a 90* plus also hold the pieces tight. Make them out of plywood.
How to use above jig
Or buy them premade, these are from Rockler