Here is how to tie a fork bow:
You will need a dinner fork (with 4 tines) and about 8" of ribbon of your choice. You can use less but it's much easier with something to hold onto. I used Razzleberry 5/8" polka dot ribbon but its a little easier with 1/4" ribbon.
First you are going to fold the ribbon in half to make a loop and put it around the fork.
Now take your back ribbon and wrap it around the front. Thread it through the center of the tines under the other ribbon.
Now just tie the ribbon in a knot (still the back of the fork) and that will hold the center piece in place.
This technique does work better with thinner ribbon, maybe 1/4" thickness.