Bill Tindall, E.Tn.
A question: Rather than slip the clamp back and forth to compress the joint, why not use two (or, more) clamps?

Quicker. Once the clamp snugs up the joint and squishes out any trapped glue it is not longer needed in this position. It is easier to loosen it a turn and slide it to another location.

Not made clear....the drawer is snugged, clamps off, square checked and adjusted by squeezing corners as needed and left unclamped for glue to cure. I want to know what shape the drawer is in as the glue cures. If clamped the drawer can spring into some other shape when the clamps come off.