Unlike water or oil stones this sharpening system never has to be re-flattened due to the flat surface being constant, float glass is the most common surface used but you can also use a bit of mdf or granite. I’ve got one of these... https://www.axminster.co.uk/veritas-glass-lapping-plate-476783
To stop the glass sliding around I use a cheap bath anti slip mat from Tescos!
The abrasive films seem to last quite a long time and when they are worn out you simply peel them off and stick a fresh sheet down. I’ve been using the sheets from Workshop Heaven https://www.workshopheaven.com/hand-tools/sharpening-tools/scary-sharpening.html
This system works well free-hand or with a honing guide, just have to be a little careful not to tear the abrasive with the blade, but that’s pretty simple once you get used to it.
Most of my one to one tuition students find this system perfect for getting started due to its simplicity and low cost.
Look out for next months Tool of the Month!