Old school dulcimer frets. Holes drilled, 12 gauge copper wire hammered into a staple, then pounded into place.
I got excited near the end and just rushed putting everything together. The copper nut I had planned was way too high so I improvised with a piece of scrap ply, will go back and redo that later. The tail isn’t finished or glued. The strings aren’t cut. I used zither pins instead of machine heads (I had a bunch and thought, why not?). Here is a pic, semi-finished, tuned to open G.
A quick sound bite right after tuning.