Embroider the design on to one peice of felt.
I found this design quite complicated to figure out so it may help to draw the design first on paper and then copy the drawing in thread. Drawing the design on to the felt will make it mucky and you will probably see the pencil underneath the thread.
Cut out two peices of felt in the shape you want.
Sew both peices of felt together. You can avoid having knots on the outside of the felt by inserting the needle into the hidden side of the felt. The final knot can be made on the outside of the felt but you can sew the cut off part into the middle of the two peices of felt to make it look neat.