Years ago, we had been given a hand-made fleece blanket and I thought it was cool, so we made several last year as gifts. Kids can help, under your supervision, with the cutting of the fleece and with the tying.
You will need fleece for either side of the blanket. The yardage you require depends upon the size of the blanket you want to create. For a sofa-sized throw, I suggest two 60"x60" pieces of fleece (one for either side of the blanket). It is fun to pick color-coordinated patterns for each side (as in the photo below). Or, you can have a color on one side and a pattern on the other.
You will also need sharp scissors. I suggest washing and drying the fleece before you start cutting.
Your first step is to match corresponding sides (each side of the blanket) together. From this point on, all cutting is done through both sides of blanket.
Cut off any frayed edges or factory markings first. Then, cut out the four corners. Each corner piece you cut out should be 5"x5". Then, start cutting strips approximately 1" wide and 4"-5" deep all around the outside of the blanket. I say approximately because as you get closer to the corners you may want to vary the width so that you won't have an odd corner strip size.
Once all the strips have been cut, make sure they are all lined up. Then, start tying, first a simple crossover and through, and then a knot. Do not tie the knot too tightly and cinch the sides up. You can always go back around and tie the knots tighter.
Enjoy your creation!