I have a A4 UV flatbed printer and I need to print over flat objects like phone cases, Keychains, Tags, Vintage physical media ..etc.

I was able to use Mailing template design in MS Word and it works good, However I'm still struggling with edges and corners. In other words, Word creates rectangular labels with sharp corners, so when I insert the artwork into the label panel I get a rectangular artwork with sharp corners, How do I configure the template to have shaped panels (for example with round corners) that correspond to the shape of the object so the printer won't print outside the object?