i've been planning to do that forever and emma's reminded me! i plan to do more too, it's really fun!
there are a few ways of course. here's what i did. in ps, but it would work in any program. i duplicated the photo first. made the frame and put it in the middle. (frame sandwich) then i deleted all but what was outside the frame on the TOP layer. then i just carefully cut out his arm (i forgot and didn't feel like going back but i'd highly recommend using a slight feather, mine's a little choppy up close). i used the polygonal l***o tool. it just lets you keep clicking in small lines instead of trying to hold the l***o tool steady. anyway, i deleted all but his arm and the poor, poor butterfly. that's it. his arm was on the top layer, then the frame, then the rest of the photo. oh, i deleted the part of the bottom photo that was sticking out of the frame too. lmk if that makes sense! Ü
here's mine again so you can see what i mean:
butterfly
i'm going to change it soon. dh thinks his whole elbow should stick out and i HATE it, but he's right! Ü