The first thing you need to do is select your photos. I printed mine at Costco. I tried some that I had printed at home but the Mod Podge made the ink run - even after it had dried for a week.
You can use either cardboard or chipboard. Since I had some boxes on hand, I used cardboard. Trace around your photo.
Cut along your lines so the cardboard is the same size as your picture.
I like to use a foam brush that you can get on sale at Michael's at 10/$1.00. Brush the Mod Podge on in even strokes. I try to keep a continuous line from one edge to the next. When it dries, you will see these lines. It will dry clear.
I put 4 layers of Mod Podge, letting it dry completely after each application. I then sanded the edges, rounded some and left others pointed, really that is your choice. I also put a layer of Mod Podge on the back just to seal it. After I finished sanding, I put another layer of Mod Podge around the edges, again, just to seal it.
I think these would be really cute with a patterned scrapbooking paper mod podged on the back.