Lay out the piece of upholstery that you are using for the back of the chair. Mark the desired spots where you want to place the tufts on the cloth, using tailor's chalk. Attach the upholstery to the back of the chair.
Run embroidery floss, five pieces at a time, into the eye of an embroidery needle.
Sew a 1/2-inch stitch on each chalk marking and run the needle through to the base of the front of the chair, pulling tight enough to create an indent in the back of the chair where the tuft is forming.
Run the needle to the back of the chair, still holding it tight to keep the indent, and bring it out the the same chalk marking with 1/2 inch of extra floss sticking out.
Hold the extra 1/2-inch of floss and knot it so that it is pressed right up against the upholstery.
Repeat the process on each additional chalk marking.