Tuck the Trinket and the cable up next to the switch. The top of the trinket board should not protrude above the switch so it will need to be placed at a slight angle. Put some pressure on the cable so the edge of the Trinket does not overlap the side of the pedal base.
Now you should secure the cable. I suggest some hot glue between the black part of the Mini-B part of the cable and the switch. Also place some glue where the cable hits the right part
of the pedal base (circled red in the picture). Sugru would work very well also but you need to keep the parts in place until it sets. Do not let the top of the Trinket board get above the switch or it will be hit by the pedal top.
Here you can see the hot glue in place. When replacing the spring, it should not touch the Trinket. To be sure, I used a small piece of electrical tape.
Place the spring on the raised circle on the pedal base. There is also a raised circle on the pedal top that you'll need to mate with while you bunch the halves together to put the hinge pin back in. It is not hard but you have to exercise some care.
Matching the raised circles on each half of the plastic with the spring, compress the spring (making a plastic sandwich of the halves again). Align the holes in the bottom side with the hinge pin.
Note the hinge pin has a narrow part closer to one side than the other. Make sure this indentation is placed towards the side circled in the picture above.
Slide the large metal hinge piece through the holes while you compress the two halves between your hands. Just a bit of metal sticks out of each end. If you let go, the switch whould stay together and click when you compress near the top.
If you have the large hinge piece in and oriented correctly, then when you turn the foot switch over, the tiny pin will fit back in the hole shown. You might have to adjust the large pin back & forth a bit to get the tiny pin to fall flush with the back. If you inserted the large hinge pin backwards and the tiny pin does not fit, no worries, repeat the disassembly and reassembly steps.
Now place the metal back plate on and screw on with the two flat screws. This will hold the tiny pin in place which holds the larger hinge pin. The back plate also provides a tough surface for the switch.
That's it, all assembled. Alot of steps were used to show the process, although the build is rather easy and does not take much time.