How to keep every graphic at 4200 x 4800 with a transparent background

The two things that cause the most back-and-forth on a print order are the wrong canvas size and a background that isn't actually transparent. Solve both once with a template and you'll never think about it again.

Canva is the easiest tool for this. Set a custom canvas size of 4200 x 4800 px, build your design on it, and save that as a template you duplicate for every new shirt. Canva's free plan can do this, but the paid plan's background remover makes cleaning up transparent PNGs much faster — worth it once you're posting regularly, even though it's an extra cost to start.

When you export, choose PNG, not JPG. JPG files can't hold transparency, so the entire canvas prints as a solid rectangle behind your design.

Before you upload, zoom in on the edges of your canvas. If any part of your artwork touches the very edge, pull it in slightly so nothing gets cropped in print.