Plastic canvas is a fun material that you can use to create 3 dimensional embroidery.
26.5 cm x 34 cm
Basically you can just use knitting yarn. Use a blunt needle. You dont hva to poke through the material. Use an embroidery needle with a large eye, because you usually work with a quite thick yarn.
You can cut Plastic canvas with scissors. Note: Use an old scissors because the scissors become blunt quickly.
You can glue the back with fabric glue. Gluing is particularly useful when you make an object made to be used because the threads do not go so fast fraying.
Also, you don't have to make lots of knots and the back looks neater.