There are few ways you can go:
- Buy used foilboard that fits your foil or is easy to mod to fit.
- Modify old surf or wakesurf or skim board - I modded one myself using Slingshot Space Pickle. It is a good size board even for a beginner
- build your own. You can build simple board from plywood, but making a nose rocker can be tricky. A bit of styrofoam, glass and epoxy and some labor works as well.
Here is a simple board I built for my Spitfire foil the last year. Used 1 inch thick insulation foam board, foot strap inserts, Garolite tubes for reinforcement of mounting holes, fiberglass and some carbon patches (stuff I had in my garage at the time). This one is too small for a beginner though.
Lines on the front deck are cuts (~3/4" deep) to allow for nose scoop build.