I recently bought cute stickers for some friends and wanted to put them in a nice envelope for gifting. Instructions for this type of envelope/tato can be found here: https://doitandhow.com/2019/07/19/pinwheel-origami-envelope-fold (the German text in the top right simply says 'Fold an origami envelope'.)
Unfortunately, the instructions are a slightly blurry image instead of a clear diagram, but on other websites, I could only find instructions where, after having folded the very first cross, you're left to roughly guess two thirds of the diagonal length (or measure the point with a ruler) instead of being guided by already existing folds in your paper... Also, the last step (folding the last flap up and slipping it under the right flap) is not shown in the image, so if someone finds better instructions where you don't have to guesstimate while folding, I'm more than happy to update this post!
I used 13x13 cm paper and the resulting envelopes are almost 7x7 cm.
