On Friday, 30 August 2019 18:12:38 UTC+1, Bert Coules wrote:
Having just made my usual abject mess of laying a single course of bricks
(atop an existing low wall) I seriously wonder why I didn't simply stick the
damn things in place and fill the gaps with more of the same adhesive.
Centuries-old technology may be all well and good if you can manage it, but
for some jobs there are better alternatives.

The secret is in an even bed of cement and plenty of plasticiser in the mix.
You can get a special tool that lays an even cement bed. eg

https://www.youtube.com/watch?v=9tBJyn_-Bns