I'm not going to include my usual architecture diagram because this device is pure simplicity. It's just a Feather Doubler with a 7 segment LED FeatherWing (in the color of your choice), along with a Feather M0 WiFi with an OLED FeatherWing on top (for debugging output). You can get all the parts you need from the shop - see the list at the right. You'll also need a soldering station for the light soldering needed to put the headers on the boards and the LED block onto the Backpack.
Here are the components after soldering but before assembly: