To save time and frustration, I decided to re-purpose a used chewing gum tin to make a jig so I could solder multiple boards at once and keep my components from moving about.
Step 1: Prep the Tin
Place your PCB on the underside of the tin and draw around it.
Make the line about 1/8" thicker on the inside to give you a cut guide.
Cut the bottom of your tin out (I used a Dremel).
DANGER! The edges will be sharp, so make sure you file and sandpaper them afterward to dull them a little. Even then, they can still cut you so use caution with your jig.
Step 2: Foam Is the Magic Ingredient
DANGER! Soldering can get very hot, so choose a foam that is flame retardant. It's better to play it safe than to explain to people how you burned your house down.
Step 3: Populate Your PCB
Then squish your foam in the top of the tin and close the lid. This will hold all your components in place while you solder them.
If you have large differences in height between you components you could also cut you foam to match this, so that there is less foam over the taller components. I didn't need to do this since my components are similar heights and the memory foam compressed really well.
Don't forget to close the lid. If it won't stay closed, use some tape or a maybe a rubber band to keep it shut. You could also reduce the amount of foam at the cost of your components being able to move about a little.
Step 4: Use Your Creation!
Because my boards are designed to be a tiny footprint some of the solder pads are very close to the edge of the hole. You can mark this and then file the hole out accordingly.
The jig gives you the freedom to move to work around to get the best soldering angles, but because the lid in this tin is curved, it's not the most stable surface (this bigger tins are flat on top so are not a problem). To remedy this, you can put the tin in a clamp, tape it down, or stick it on some modeling clay (which is the method I used) to stop it from moving around.
Step 5: Enjoy the Fruits of Your Labor!
I took the opportunity to snip the component legs while they were still in the jig.
All that remained for me was to snap apart the 3 PCBs into individual amps.
Job done :)