What did you use for backing? And if you used a backing, what type and can I use just monkey glue? I was going to make a template of the space and then glue the corks to the template and then glue the template to the wall. Your thoughts?

Backing is not necessary if a good adhesive is used, although it may be helpful to paint the wall a similar color as the average cork to account for any gaps that might arise here or there. I'm not familiar with monkey glue, but in this case a regular construction grade silicone adhesive was used, I believe. I'm not sure a template is necessary to achieve the effect shown here; the stacking went organically row upon row directly up the wall surface, introducing small errors in the tessellation that brought about interesting irregularities.