This is so easy to do, you won't believie it! Insted of putting your 4x6 photo on the paper then trimmind it, you trim the photo in stead!
First you need a piece of 12x12 paper of your choice, then cut the paper in half. ( now you have two 12x6 strips) Take one of the strips and cut it 4" two times.( now you have one 12x6 and three 4x6 pieces of paper) Repeat on the other strip. (now you have six 4x6 pieces of paper) Next, trim your photo 1/8" on all sides, or 1/4 on the length and width.(now you have six 4x6 pieces of paper and one 3 3/4"x5 3/4" photo.) You cut so little off, you cant even notice it! Then glue the photo to the mat (4x6 piece of paper) Now you have SIX mats using just One 12x12 paper! I do it with all of my LO.