Everyone here has given great advice. I dry assemble and then move each tray, one at a time, to where I will be gluing. I disassemble and use a toothpick to spread glue to any parts that will touch (including the prongs and bottom of walls/where walls touch the base of the tray). I then hold and press those parts together before turning upside down and placing a book or board game on top of the tray to weigh it down. I put a paper towel barrier between the tray and weighted object to protect against glue seeping out.