They were these from B&Q but they are no longer available, but other similar products seem to exist elsewhere. There is an installation video on that webpage. I would say he ain't putting on anything like enough adhesive for each step !
https://www.diy.com/departments/geom-st ... 077_BQ.prd
They were about £90 (for 3 steps) when I bought them (even more now) so not cheap but were very good quality, engineered plywood with a real oak veneer and a solid oak nose, all nicely finished, i.e. no oiling or varnishing to do.
I cut to length with a powered mitre saw, and then I cut them to width with a jigsaw, then stuck then down with tons of building silicone which makes up for any imperfections and gives a slightly softer flexible step. The stair nose is designed to fit nicely if you don't get the cut perfect on the risers.
I messed up twice with my measuring though, so that was another £90 as they only came in a pack of 3.
I was concerned about whether they would be too slippery but we've never had an issue.