Never buy only the headboard. You may have to pay a premium price, if you happen to purchase just one headboard for your bed, because headboards are sold in sets. There are simple measures, and if those are followed rigorously, you can always create a good matching headboard for your full sized bed.
1. Begin with measuring the distance between the floor and top of your bed.
2. Now cut two headboard strips which are perhaps 30 inches more than what you had already measured.
3. Use sand paper to clean the headboard strips.
4. Use a wooden plank, and attach the strip on the plank. Use nails to attach the strip onto the plank. Make it firm so that plank holds the strip tight.
5. Again put the second plank over the strip to complete the headboard.
6. Paint the headboard with a matching colour to give it a refreshing look.