We can make a neat little enclosure to hold the circuit, microcontroller, and battery, as well as provide posts onto which to clip the leads coming from the detonator.
I modified a small wooden box I got at the thrift store for $1.97, but you can use any type of non-conductive enclosure you want.
Mark for holes on your box, leaving some room from the interior walls for the nuts to fit.
Drill out the wholes with an appropriately sized bit.
This is a good stacking order for the posts, with the screw and first washer of each going inside the box, and the remaining hardware on the top.
Drill out and/or chisel a hole for the panel mount USB extension to fit.
Plug the LiPoly battery into the Feather's battery connector.
Wrap the wires for the AC input on the FeatherWing Proto board onto the posts on the inside of the wiring box. (Alternately, you can us crimped spade lugs.)
Connect the FeatherWing onto the Feather, plug the USB panel mount extension into the Feather, and place them and the battery inside the wiring box.
Leave the relay wires running out of the box, and then close its lid.
Connect leads from the terminal posts on the wiring box to the posts on the detonator or other AC source.
Strip some insulation from the ends of the relay output wire coming from the wiring box, and screw them into the screw terminals on the power strip. Polarity matters here, so make sure you follow your color coding.