Follow this page for the assembly of the NeoTrellis tiles.
NOTE: there is no need to solder wires to pads on the board if you use the Feather RP2040 as you can use a STEMMA to STEMMA QT cable instead.
I2C Address Jumpers
Solder the I2C address jumpers as shown here. This gives you addresses 0x2E, 0x2F, 0x30, and 0x31
This guide page shows how to assemble the acrylic case for your NeoTrellis 8x8.
NOTE: You can skip the steps involving switches and battery as this will be used as a plugged-in MIDI controller over USB.