Cut the legs out as shown in the photo. They should be a little shorter and narrower than the body.
Make all cuts at a straight angle. Clean the blade of the knife after each cut, so that it doesn't pull the paste down when cutting. Smooth the sides with your finger.
Position the legs so that they are standing and check if the legs are not leaning to the front of back (they need to stand straight or else the topper will be leaning to the front or back). The top of the legs needs to be flat too so that you can attach the body properly.