This is going to be long and wordy but I know I work well with very specific instruction so hopefully this will help!
Step one: Cover your buttons! This is such a pain the butt, especially with a thick upholstery fabric. So you know what? Tim and I said screw it and hot glued the fabric on. You can use the press too - Either way looks great in the front and is holding up well. I covered 43 buttons in the span of a few Grey's Anatomy episodes.
I worked kinda in rows from the center and kinda up and down. I personally didn't worry too much about getting the perfect folds in the fabric. Finally when the buttons were all in I trimmed my fabric and attached to the back with staples. Tim was able to easily attach it to the wall using screws and the fact the board already has holes in it. We're about a week in and it is holding up really well and I still stop and stare at it every time I walk in my room.
Things I would do different next time:
Use smaller buttons, maybe 3/4" or even smaller.
Burrow actual holes in the foam for the buttons to sink into. Maybe using a foam punch tool.
Do more of a "hospital" fold on my corners.
Supplies and price breakdown for my king sized headboard:
Peg board - $15
Foam - Free on trade from my mom. Similar found on Amazon for $50+.
Upholstery buttons - $20/for 50 purchased from my mom. Similar found here for $40+.
Fabric - $26/3 yards of upholstery chenille on clearance at Joann's.
Other possible purchases if you don't have or can borrow:
Long upholstery needle
Cord (I used cord exactly similar to the kind you find in blinds. It was perfect for pulling tight and having a good hold).
Random small buttons
I am so in love with the way our room is shaping up! Stay tuned for some amazing ikea hack nightstands coming next week. My Country Chic Chalk paint arrives today and I am so excited to dive right in.
If you have any questions feel free to ask in the comments! I would love to hear of you try to make one of your own. It's really pretty easy once you get going.