Frame It Easy , 3 reviews
This is one of the few print on demand companies I found that include matting options with your framed print! Bonus that the quality is some of the best you'll find anywhere. The app installed pretty quickly, no stalls or hiccups. A minor thing, you have to select your options first then click preview before you can see a mockup. I think they're working on that. Be aware that you can create an insane amount of variants so it's a good idea to plan out your sizes, frames and options beforehand.
The Frame It Easy app makes passively selling my framed art super simple. Straight-forward set-up, easy-to-follow steps, and an overall seamless experience with responsive support. Highly recommend.