What others have said. It's a great start but I think you'll want to train more to reduce the gap and also get to a point where you feel perfectly confident you're not going to ruin your neck's fingerboard.
There are different levels of complexity too:
- flat piece of wood w/o frets: easy to sand flat/smooth
- fixed radius piece of wood: harder but still easy with a radiused block
- fixed radius with frets: lot more fun
- compound radius with frets: harder than fixed radius if done on an unfretted neck, no different on a fretted one.
Is your neck already fretted ? If so I would suggest maybe getting one of these horribly cheap neck knockoffs on eBay to practice on a garbage neck you don't care about. Got one for $20-$25 shipping included a year ago. Can't seem to find them that cheap now though. The thing was absolutely terrible for doing anything musical (frets not parallel to each other, etc) but fantastic for practicing inlays, veneering, etc...
Without forking for one of these you could probably use a radiused piece of wood and "simulate frets" by putting some piece of woods restricting the amount of space you have to sand those inlays flat (which is what you'll be forced to deal with on a real neck).