Cabinetry: http://en.wikipedia.org/wiki/Cabinetry

It doesn't have to be overly taxing physical work (requiring a lot of strength), but it is usually a very active physical work (requiring constant movement).

Getting well paid while doing it might be tough. It is not a well paid job by default. However, with some imagination you might be able to use your scientific/math/engineering background to make products that have decent margin.