Step 3: Tune and play
The rest is experimenting with bridge position, thread location and angles to find the best sound. After you get the string buzzing, move the string slowly up or down until you find a spot that makes it louder, richer, longer sustain or finds some other quality you like.
Patience is the key, it took me 3 times longer to tune and refine the tambora than to make it. Most of the fun and the work is the exploration of sound and it's relations in every small adjustment.
I found when tuned up the best sounds come from just barely exciting the string by running my finger over it or giving it the lightest of plucks. When playing, a clawhammer style thumb and finger pluck works well.
If you watch the video, you will see that my cat likes it. for reference my cats also like to sit in my lap when I play tuba and wanted to sniff the work while I was using the hand drill on it.