Funny you write that, I found this particular blog post via a Google search!
Although UK Standard Gauge O Scale (7mm to the foot or 1:43.5) trains will run on my track, I am actually Narrow Gauge SM32, which is 16mm to the foot or 1:19.05.
I had problems with my expansion joints, so I redid them before the winter set in, but I now have work to do to reinstate a complete loop. A target for 2021 is to make at least one of the stations not look like an apocalyptic wasteland.
Great advice and I have read about DIYers struggling to get slate to adhere to concrete. If I get the time, sunshine and slate, you'll see some Flickr progress in a month or 2 (or maybe 3 or 5).
Likewise, keep cosy and stay safe!
Alun