Here is my inspiration photo.
I started out with a couple sheets of posterboard. Cardboard or foam core would work too. Whatever you have.
For the sides of the chest I cut a rectangle approx 10" wide and 8" tall, then cut off the corners to make the top wider than the bottom.
I also made 2 half circles, the diameter of each the same width as the top of the side pieces (8")Once I had the sides for quidelines, I measured the angled pieces and cut a series of rectangles for the rest of the pieces. I decided I wanted the chest 15" wide, so that is how wide all the rest of the pieces will be and the other measurement corresponds to where it fits on the chest. The width of the bottom piece matches the bottom of the side piece (approx 7"), the front and back match up with the sides on the side piece (approx 8 1/2"). I cut the top piece slightly larger than the round part of the half circles, again, at 15" wide.
I added an extra piece of posterboard (using spray adhesive) to the top piece in the center, then punched holes through both and ran a piece of yarn through it for hanging.
Now it's time to assemble! Using small tape pieces I took one side and just started adding pieces. Once the pieces were in place I went back in with larger pieces of tape and fully covered every edge with tape.Assembling the top as one piece and the bottom as another piece, then joining them together from the inside at the back and sides. I left the front open so I could stuff the pinata later.
On to the decorative part! I simply took a roll of crete paper and using spray adhesive, applied it in overlapping strips (you could also fringe the edges, but that's a whole lot more work). Once the entire thing is covered you can go back and trim the edges and put on one more strip of crepe paper to make it all clean and pretty.
Time to add the prizes!On any other pinata I would have left a small tab opening on the side to stuff the items into. As the design on this one worked better to just leave the front open and it's hard to get tape inside to adhere it as we did the other sides I fudged it a little by punching a few holes and kind of lacing the front together with yarn. You hardly notice it and could cover it up with decorative items later if it bugs you.
It was a pretty simple matter to add the lock and the trademark sword on the sides. I just free-handed something that kinda, sorta, resembled them onto some golden yellow cardstock and cut them out.And there we have it! A fully assembled treasure chest pinata in under an hour and probably less than $2 in materials (not counting prizes). Yay! Next on the list - party favors or games...