We have recently put a lot of resources into face frame manufacturing. Most of our work is flush inset and a lot of that uses fully mortised butt hinges. This is a lot easier to do if the face frames are really square.
Our wide belt sander is 42 inches wide but about 20% of the frames we build seem to not fit within that constraint. Rather than have some of the frames hand sanded and some of them wide belted we developed systems to make it so that no face frames had to be wide belted after being pocket screwed. We do have to have to kiss the joint with a random orbital sander to deal with grain raise from wiping glue but this is way better than also having to sand the cross grain marks off the frame. It's also easier for inexperienced people to be successful.
Our protocol is to polish sand the exposed face on the wide belt then, with this face oriented down, we run the stick through a dedicated planer that always produces 24mm thickness. This planer has a spiral head so produces a fairly clean face. With this system we know that every part is the same thickness every time.
The cross grain dimension is wide belted to thickness as needed. This is the weakest part of our system so far but we can usually absorb minor variation at this step. We have an idle shaper that will eventually be set up with a fence away system for controlling the cross grain width.
After the parts have been chopped and drilled for pocket screws the sticks go onto the face frame clamp. We have a Ritter that we bought from one of the other guys on this forum. The Ritter beam came with three clamps but we only use the bottom one. The other two are actually in the way. Eventually we will will pull them off and use them in some other process.
The Ritter Clamp easel is made out of steel with a grid of holes to position. This seemed to work but any excess glue that was left on the table seemed to weld itself to the steel.
These lumps of glue, albeit small, were the root cause of needing to wide belt the frame after assembly. Our solution was lay a piece of plastic laminate onto the table and glue a strip of laminate to the three fences. The plastic laminate makes it really easy to clean up glue after the frame is made.
We replaced the air pistons that push sideways with magswitch clamps. These have about 150lbs pull and reach right through the plastic laminate like it wasn't there. The clamps hold the parts in correct alignment and the endgrain always lines up perfectly with the side grain.
The extra attention we pay at this phase makes door fitting quite a bit simpler as well. We added a bunch of new clamps recently to facilitate building these frames in a bucket brigade. An experienced person sets up the parts while an inexperienced person drives the screws home and mops up the glue.
This bucket brigade approach has helped us add inexperienced people to respond to the current surge of customers. The new people become useful on their first day.