Is your egg crate a series of individual boxes, or do your dividers cross
and interlock to form the boxes?

They criss cross. For example if I wanted 9 squares I would use four
strips of plywood oriented like a tic-tac-toe board. I use the table
saw to create slots halfway across the width of each strip. Then they
fit together and the whole tic tac toe board is dropped into the
drawer. No need to anchor it to the drawer. If you ever need the
drawer for another purpose, you can lift out the tic tac toe board.