I learned this from a fantastic fibers artist Mimi Smith. Mimi is fantastic with all things fiber!
I often do this with my after school kids and they love it. I also use the seven strand braids in making my silk flower and shells hair falls that I sell on my tribaltrends etsy page.
Step 1 Is finding a cardboard box to make your disk from. I have found that Macaroni and cheese boxes are just the right size for this. Cut out a square about 4 inches by 4 inches. Its about half the size of the large box panel if using the mac and cheese box.
Step 2 Cut a trianglar wedge out of the corners of the box. You should be left with a octagon or "stop sign" shape.
Step 3 Cut a small slit about a 1/2 inch long on each side of the disk.Carefully point your scissors through the middle of the disk and cut a small hole(slightly less then an inch)
Step 4 Cut seven long lengths of yarn. Keep in mind that the braid will but slightly shorter then the lengths of yarn your cut.
Step 4 Tie the yarn lengths together in a knot about 1-2 inches away from the yarn ends. Put the knot through the center hole and thread the yarn through all but one of the slots you cut.Turn the open slot facing up. Count down to the third string away from the open slot. Pull that length of yarn out and flip it over to the now open slot.
Step5 Turn the disk to the right so that the new open slot is facing up. Count down to the thrid string from that open slot again and flip it over to the now open slot. Continue this until your braid reaches a desired length and knot the end off. The braid comes down through the middle of the disk.