You should hunt down a Mr Mike Williams......builds all his own boards and with a fair old success rate too.

I think there may be a few of us Home board builders out there.

I've made a couple out of some 12 mm 5 ply, I ended up getting a sheet of "forming Ply" ( same glue as marine ply but lower grade of wood )

I cut out the shape I wanted and then layered a slightly smaller piece on top using a layer of resin in between.
Gave each tip a few inches bend about a foot from each end let if set.
Once I removed it from the jig it released about a inch from each end and I was left with 2 inches deflection each end.
Screw or bolt some footpads and fins to it and there's enough to get up and going on.

I've seen a others some guys have made some out of 3 layers of 3 ply with more aggressive curves that look like they would cut hard, the owners gave them a good rap, ( obviously people aren't going to tell you they wasted heaps of time on these things).

I think they are good to learn on but unless you are very handy and can learn from your design flaws and improve them each time, they will ultimately hold you back to a degree.
I can hear people saying " that's why companies pay millions for R&D and pro riders"

That said it is a good reason to be in the shed with beer and power tools.