I just received my order of 6 Stillman and Birn Sketchbooks which should last me 1 year and therefore worked on adding on elastic bands to meet my sketching needs.
Here are the tools I used:
Step 1: Mark the drill holes
I held onto a sketchbook cover from my previous sketchbook (Daler Rowney Cachet) to make marking the holes easier. You can easily add holes without this template. (It's roughly 3/4" from the edges)
Step 2: Drill the holes. I used a 7/32" drill bit but it depends on the what type/ width of the elastic you purchase.
Step 3: This is a very basic black elastic band (1/4" wide) I purchased from a store such as Michael's. I would cut off a piece and adjust the length later on in how it feels.
Step 4: The elastic is inserted from the outside of the book and is adjusted accordingly to how it feels when the elastic is used to close the book. Excess elastic is cut off.
Step 5: Once the elastic adjustment is made, I put a dab of glue into the hole and would tape off the elastic ends with a white masking tape.
Step 6: That's it! Let the glue fully dry off before using the elastic.