My husband uses Affinity Photo and Designer for projects involving heat pressing and I use pagePlusX9 (Ok I know its a DTP program but I find it so useful for all that I do. So between us we have just created 6 templates of actual size key fobs and coasters
We used two layers for each template, one for non printing visual guides and the other for printing positioning guide plus the artwork. These are then output using N-up printing from the Print/PDF Preview file menu to check if all is ok and the number we want to print.  All in all it works very well and PagePlusX9 lives to fight another day with our new venture.  Cheers Vicki