Place the foam pattern pieces inside the cuff and secure them with glue.  Hot glue works surprisingly well here -- the plasti-dip foam will tear before the glue will yield.  Hot glue sure loves foam and acrylic.

My other favorite thing about hot glue is it's "undo" feature: once it's set, you can use 99% alcohol to release the hold without damaging your foam or acrylic one bit.  So if you don't get it lined up perfectly the first time you can try again.

Trace your pattern details onto your sheet of worbla with a sharpie.  Pay attention to whether you're doing the right or the left and be sure your pattern's facing the correct way.  Cut them out. 

Use a heat gun to gently melt the worbla and stick it in place on your acrylic.  Smooth it down with a sculpting tool.  No need to glue, it will stick in place really well once it hardens.

Use some more worbla to decorate the setting for the Circuit Playground.  Be sure to leave the USB port accessible (plug a cable in to be sure) and don't cover up the lights or the buttons.  

Cut a slit in the foam and feed your battery cable through.  Mine was really long so I trimmed the wire and re-soldered the connector to minimize the chance of pulling or tangling.

Robust-ify the connector by covering it in 1/2" heat shrink.  Optionally put a little hot glue inside the heat shrink to be sure it's as bulletproof as you are, but be sure not to get any glue inside the connector.

Mold a strip of Worbla along the top and bottom edges, covering both the foam and the acrylic.  It will get stiff, so only do this along the acrylic, and leave the foam edges free to bend around your arm.

Glue a piece of foam to the inside near the battery cable to form a battery pocket.  

Grab your plasti-dipped straps and affix the male side of your snaps to one end. Attach the female snaps to the bracer's other edge and then glue the straps in place so they're the appropriate size.

Time to add the silver and gold!  I used acrylic metallic paint directly on the Worbla.  (My aluminum foil arm came in "handy" again for this part)  

Cut stickers out of aluminum tape and carefully smooth them on to give a metallic finish.  These will block the light entirely so be sure you don't cover the individual neopixels.