Connect a 4x4 RGB-LED programmable silicone keypad to your Raspberry Pi Pico.
The APA102 addressable LED's can be programmed in every desired colour, so you can map the keys anyway you want!
Note: you'll need to solder male headers to your Raspberry Pi Pico.
Turn the larger board over, and attach the little rubber feet to the paw print spaces on the bottom.
Flip it over again, and pop the silicone keypad over the buttons so the tabs fit into the holes. You can then slot the retainer plate over the top of the keys, matching up the key markings with those on the base board. You can install the retainer plate either way up, depending on whether you prefer it patterned or plain!
Poke the M2 bolts through the holes in the mounting plate (from the top) and screw on the nuts to keep all the layers sandwiched together. The bolts only need to be tightened up enough to keep the layers in place - if you find that the keys are hard to push or that the silicone layer is bulging out of the sides you might want to slacken them off a bit.
The labels on the base will show you which way round to attach your Pico - just match up the USB port to the markings on the board.
The easiest way to get started is by downloading and copying Pimoroni's custom MicroPython uf2 to your Pico, it includes all the libraries you'll need to use the add-ons. Click here for Pimoroni's beginner friendly tutorial!