Each drawer that has one of these divider assemblies followed the same approach.
There is a 3/4" tall, mitered frame around the inside perimeter of the drawer. The fit is so precise that you have to bend the last piece in order to get it into place and then that tension holds all 4 parts firmly in position.
The horizontal bars are 3/8" tall and a little over 1/8" thick. First, they're cut to the exact length of the inside of the drawer. Then they're taped together so I can mark and cut them all at the same time. Each notch is as wide as the part is thick, thus allowing the mating piece of lock over it.
Same approach for the vertical bars.
Then just round over the sharp edges and put it all together.
The middle 3 drawers are deeper, so there was room for a sliding till to ride on that 3/4" mitered frame. No sense wasting drawer space!