The lower board will be glued into the storage box, the upper one somehow needs to rest on the lower board or pots. The 5mm MDF stands no chance though against the weight of a fully loaded board of paint pots. So I constructed a frame for the upper board.
Once glued and nailed, I placed the upper board on the frame and hit it with a hammer a couple times. This imprinted the nail heads, sticking out below the upper board, into the frame.
All those imprints where then drilled into, to create a depression for the nail heads, so that the actual MDF board would sit on the frame, and not just the nail heads.
