I took the Wilton cake decorating classes. The first level kit came with full sized images that we had to take to get laminated and then piped directly on. You can scrape them off and practice over and over again. You could laminate your planned design or place it underneath parchment paper and practice that repeatedly. (No need to make cake or cookies to practice!) It doesn’t look like the Wilton books are readily available anymore, but I did find these, which you might find useful if you wanted to also practice your shells and trims- https://www.amazon.com/KDDOM-Decorating-Practice-decorating-drawings/dp/B08ZY7R49H Look for „cake decorating practice“ to get more examples. And it looks like some of the extensions might have some of them, too- https://extension.usu.edu/saltlake/files/BegCakeDecorating.pdf
