Step 1: What You'll Need
One piece of red foam
One piece of sticky back white foam
Something with a circular base slightly larger than your koozie or cylinder
Step 2: Cut "Stripes"
Step 3: Make the Base
Step 4: Cut Out Circle
Step 5: Apply White Stripes to "Hat"
Peel the backing off the sticky side and apply to your cylinder/koozie.
It doesn't have to be perfect - wonky is actually more "Cat In The Hat"-like.
I put mine so the seams were in about the same place on the back side of the pencil/pen holder.
If desired, secure the ends with foam glue.
Step 6: Apply the Base
Center the circle you cut out on the cylinder and glue down.
Let dry, then fill with pens, colored pencils, markers, etc...