Start by desoldering the wires on the speaker, then solder on longer, more flexible wires facing "in" instead of "out," so it will fit inside the dome.
The speaker press fits into the dome, then thread the wires through a hole on the collar. Don't glue anything in place just yet.
Solder long wires onto one of your LED sequins (different colors for positive and negative is helpful), and thread the wires through another hole adjacent to the speaker dome.
Before you begin assembling the main "brain" chunk of circuitry, strategize a bit. The boards will go together in a stack inside the "battery" pouch, and there isn't much room from side to side for extra wire. Use the mounting holes to route wires through to different layers.
If you're using a metal snap closure for any of your collar's pouches, insulate any metal that could come into contact with the board with tape or glue.
The Bluefruit Micro and Audio FX boards share power via the connectors on the backs of the board (usually used for attaching a JST port). First tin the pads and the wire ends, then use tweezers to hold the tinned wire in place while you reheat the solder to make a solid connection.
Assemble the rest of the circuit according to the diagram, soldering small bits of wire to connect the boards' pins. Try to use short wires, but don't make them too short or that you can't see between the boards to double check your connections or troubleshoot.
Once your circuit sandwich is complete, you can wire up the components that are elsewhere on the collar.
Thread the speaker and sequin wires into the main circuit compartment, and strip, tin, and solder the wires in place according to the circuit diagram.
To attach the map light sequin, cut off the JST connector from your battery pack (it should be off and/or empty), then solder two wires onto each the positive side and the negative side. One set of those wires goes to the sequin, and the other set will travel through the collar to the main circuit compartment.
Tape the map light sequin to the battery pack near the center, and place the battery pack in the leather "tracking" pouch. Adjust the position of the sequin to your liking.
Phew, almost there! You haven't glued anything yet, have you? Ok good. Clean up your workstation and double check there aren't any bits of wire or metal hanging out in your circuit compartment, and position the boards so they're not touching each other.
Test the circuit and be sure it is working before proceeding to the more permanent steps below!
Only after checking that the circuit is complete and in working order, you can stick the layers of the circuit sandwich together with foam tape and close up the pouch.
It's also time to glue down the "talking" sequin and its dome, as well as the speaker dome.
E6000, shoe goo, and other permanent adhsesives are suitable for this project, but hot glue is not durable enough and so not recommended! Use a toothpick for precision application and wipe up any excess with a damp cloth.
To secure the wires on the inside of the collar, you can glue a piece of fabric to cover them, or stitch them down with a needle and thread-- your method will vary depending on the material of your collar.