I had a small adapter board, where I wanted to isolate the bottom of the board. A good time to see if epoxy would work.
First, I used electrical tape to build a form. I had no idea if it would work, but seemed like a good idea. I also had two mounting holes. I used two small plastic pipes, I cut from a Q-tip to fill the holes.
The top of the PCB, I also covered with electrical tape.
Now I used 5 minute epoxy (which was by the way >8 years old...) and some carbon black pigment to make the epoxy black.
Then I filled the form with epoxy
After some minutes, I removed the electrical tape from the PCB. It was removable very easily without any residue!
Some epoxy found it's way through the form though...
But with a sharp knife, it was easily removable. I also drilled the holes again to clear the hole (not seen in the image).
I had to remove also some epoxy on the back. It looks like the epoxy filled one side too much...
For a first try, it turned out pretty good!