How to do it
Stretch the foam and sheet combo around the headboard so it is even and firm all around. This will make attaching the patterned fabric easier.
During the process of attaching the buttons, sit headboard upright on the floor so you have access to the front and back at the same time. Be careful to not pull your thread too tight when attaching the buttons; if you pull too tight, the upholstered fabric may run or rip.