The other day I went to a local lumber shop and asked about melamine. I wanted a light, waterproof top for my table saw, where I could set down drinks or use liquids, so they won't soak through to rust the cast iron top. According to the guy at the lumber shop, melamine is not waterproof. It feels like plastic to me, but he says it will soak up water and swell. I asked, "It feels like waterproof plastic to me, are you sure?" He said, "Absolutely yes."
I agree with @GeorgeC
's suggestion: Go to a countertop store and ask for a scrap piece of granite. That is what I did, and they gave me one. I told them the dimensions of granite that I needed to flatten a #7 hand plane and why I wanted it.
In my opinion, the real trick to sharpening is being able to set the bevel angle you want, perfectly and consistently every time. I use the Veritas Deluxe honing guide set, which is expensive, but nice. Before that, I learned to match the bevel angle with the inexpensive honing guides by pressing the bevel on the flat marble/glass surface, then seeing where the honing guide wheel aligns with the edge of the flat surface. The edge makes it easy to see if the wheel is too high or too low. Take your time and be picky.
I built setting jigs out of flat pieces of wood but they didn't work out. Setting the honing guide with them was not consistent enough for me. I just learned of a different setting technique: Drill a flat-bottom hole to a precise depth in a scrap block and use the hole to set the honing guide. Simple and brilliant!