I've started putting together a cheapie fretless for myself. Not much money to do it properly yet but I can't wait any longer...
I picked up a cheap all maple neck and a mahogany body with a trans red finish recently as the basis for the build.
The body is OK aside from a small ding and needing some polishing - it's new, but has been bumped around a little. The neck was sealed but not finished and good thing too - the heel was about 2mm wider than standard. So I trimmed the heel down to fit and removed all the frets quickly. Once the frets were out a problem surfaced - a bad lateral twist to the neck. So I grabbed a 12" radiused sanding block and levelled the fingerboard as far as possible. I couldn't get it perfect because I had to remove a lot of wood and the 21st fret side dot started threatening to show through the top of the fingerboard. Close enough and it's only a temp neck anyway... I sanded off the rest of the poly sealer up to 220 grit and resealed with tung oil and left overnight.
Today I squeezed some plain old imbuia wood filler into the fret slots and have left it to dry thoroughly. If I were doing this properly, I'd use a dark epoxy filler to help regain the neck's stiffness that it's lost without the fret compression, but once again, I'm not too worried for temporary use on this guitar.
Pics so far:
The pickguard is just a spare placed purely for illustrative purposes - I'll get a black guard and it'll need to be a 2 humbucker or a humbucker/single for the pickup. Bridge pickup will be a DiMarzio Multibucker (purely because I have one lurking). No neck pickup for now, but I'll eventually fit a Sustainiac, so the driver will then be in the neck position.
I'll put another thin coat of tung oil on later to seal the filler then spray a coat or two of nitro. Nitro isn't really durable enough for fretless, but once again, OK for now... The final neck will probably have an ebony or pao ferro board - stiff and hard and needing no finish.
For now to get it up and running, I'll have to get a set of tuners, a bridge, a neck plate and a jack ferrule. I'll probably just get some cheapies from Guitarfetish for now (unless I can scrounge) and upgrade when possible. Everything else I have.