Cardboard
Use cardboard to mock up your enclosure, then fold the mock-up flat and you can work on assembly more easily than trying to solder within a 1590A (or even larger) enclosure.
Too-long wires get in the way, but just-enough wires don't allow wiggle room for getting the circuit inside the box (and out, down the road should you want to modify/repair).
Further to the ol' in/out in/out, me Droogie, I no longer use this type of power-jack:
The jack is inserted from the outside in, nut fixed then soldered.
They look great, very finished appearance on the outside of the pedal and come in all sorts of colours (yellow, red, blue, white), too...
However, once soldered, you can't easily remove the circuit from its enclosure, not without first de-soldering the jack.
I use external-nuts for everything now, with wires long enough to make getting the entire circuit in/out of the enclosure a doddle.
Pics courtesy
GuitarPedalParts, no affiliation.
As with everything in life, there are trade-offs. They don't come in crazy colours, only black, and they look ugly protruding outside of a pedal with the clunky nut...
I'm just building for myself and a few friends, so functionality wins over aesthetics. If you received the innies in your kit, I'd recommend ordering a bunch of these and some spare capacitors and resistors for the inevitable additional builds down the road and mods etc — keeps the shipping costs down when you buy in bulk, if you've no brick&mortar shop near you with such minutiae.
Great choice in the Hjärt Müller, I've wanted one of those since ... since before Moody discontinued the Mewtron kit. I should've snagged one of the last two in stock — how was I to know it'd be discontinued? MOODY! BRING BACK THE MEWTRON!
Welcome to the deeeeeeep end of the pool, BassBrad...
DIVE IN!
The water's fine...