white polymer clay
x-acto knife or steel blade (like shown in the picture)
small round cutter or straw
ultra fine point sharpies in blue and red
You can do this using a pasta machine
(I used the thickest setting)
you can roll by hand with a rolling pin.
Just flatten the clay!
You do not want it to be too thin and fragile, so pick a thickness that feels sturdy.
I centered the first hole, then placed the other two closer to the top and bottom edges. Look at a real piece of notebook paper as a guide.
You could probably use an air dry clay also, but just make sure to use a thickness that is not too fragile or breakable.
To do this, I looked at a piece of notebook paper as a reference.
I left a bigger space on top (about 5/8 inch) then, with a ruler, marked increments of 1/4 inch. You want to have enough space to write, so don't put the lines too close together.