I don't know a website but I do know how to make them. Hopefully I can explain it to you. Easiest is to use 5 " squares from a charm pack or cut your own. You need 5 pieces or 6 if you want to add batting(which i do as it makes them a bit stronger). Fold 4 pieces in half(iron or finger fold).If using batting I take 2 pieces of squares and sandwich a piece of batting in between and sew an X across them with right sides out.If no batting the bottom (5th piece) will be facing up. Start to lay your folded pieces with finished edges in/raw edges to outside on top of bottom or 5th piece. The next piece lays across half of the previous piece so it looks woven. Make sure the pieces are close together in center and edges are lined up with your bottom piece. I f using batting, I use my walking foot and sew all around edges with a 1/4" inch seam other wise use whatever foot you use for piecing.Once that is done you just start turning it inside out. Keep turning until it is flat , push out your corners and press. Hint: if using a print that has a design you want on top, lay that side face down as that will be the side that becomes the top.
If needed I could prob come up with pictures for you.
Hope that helps