The authentic Montessori addition strip set is bigger than this but again, I used what was handy. I found a 8.5" x 11" frame at the dollar store and based the size of my strips on that. This is the addition set. I will get to making the subtraction strips down the road so check back for pdf for that!
Print off the pdf for the board and insert into your frame.
Print off the strips - one set on blue paper, one set on red paper. Trim off excess (but leave a bit of space around for trimming allowance) and spray glue onto your card stock.I was lucky to find some really thick card stock at my local alternative art supply store. They were cast off book covers so I liked that the strips would feel thick like the real Montessori wooden strips. (However, they took me a while to cut through...) Tape over with clear packing tape as way of providing some protection for ink, and it'll make these a little more durable and wipeable.