I've seen some builds where they use zip ties as frets for simplicity
I've built a total of six of them so far, all with 1, 2 or 3 strings, none of them have frets or dot markers, 1 kept, 2 I sold and 3 I'm selling, haven't had any problems myself and the customers haven't complained.
As long as you're good with a slide and know the scale length, frets ain't needed on a broom handle.
I'd put small marks along the top edge
Thanks JL - Great Idea
Broom handles are a great nod to the past,not to mention economical.