Model t-shirt mockups (with transparent background) generated with Printful‘s Design Maker. Layout using Affinity Designer. Final designs exported from Affinity Designer to JPEG format with Quality set to 100/Progressive. Then, exported JPEGs converted to WebP format using EZGIFcom‘s JPG to WebP converter.
Affinity Designer v2 now has a direct export to WebP (which I need to try out instead of using EZGIF.com).