Step 1: Start
Toilet roll or baking paper cardboard tubes
1 x carboard box
Roll of string (wool is fine) OR sticky tape (lots)
In this instructable, I will give you an idea you can use for your own cat carry box. A window that your cat can get fresh air and see well through.
First thing is to grab that box and cut a rectangle/square out of the side. This will be where you want the window to be. Make sure you keep the peice you cut out intact in case you need it for something later on - an add-on, maybe.