Amazon.com: Silicone Cup Cradle for Tumblers with Built-in Slot, Tumbler Holder for Crafts Use to Apply Vinyl Decals for Tumblers, Small Tumbler Stand Cup Holder with Felt Edge Squeegee for Cups Bottles(Cyan) :
DIY Vinyl Decals for Tumblers: Cozy Fall & Winter Sayings! - Jennifer Maker
DIY Tumblers with Color Changing Vinyl - Persia Lou
How to Make DIY Vinyl Decals for Tumblers - Semigloss Design
How to apply a decal to a tumbler so its straight every time - YouTube