How to do it
Copy the template onto felt. (Front and back). You may use a 24 hour disappearing pen.
Cut out the front and the back.
Sew the front and the back together using tacking stitches (for example embroidery floss, either all threads or 3 threads for clear stitches).
Fill the monster with polyester stuffing as you go along. Make sure to fill all the details (you may use a knitting needle).
Finish the sewing and fill with the last bit of polyester stuffing.
Cut out details from felt using the template and attach with Craft Glue (you may attach small pegs to keep in place whilst drying).
Add details with textile markers and 3D-Liners.
The finished result could look like this.