How to sew arms to a crocheted toy and make them movable
You just need a strong thread and a needle long enough to pierce through the body.
The main idea is to stuff the body of your amigurumi very well and to pierce it through the same points all the time.
With a strong thread (I use DMC Perle Cotton #5) in a few strands connect one hand. Don’t make any knots just leave a 15 cm thread end from the inner side of the hand. Push the needle from the inner side of the hand to its outer side, make a small indent and push the needle back. Pierce through the body.
Connect the second hand. Push the needle from the inner side to its outer side and then back. Push the needle through the body towards the first arm.
Make sure that you pierce the body in the very same points and the arms in different. It will help to connect arms firm but will make them movable.
Pull both ends hard and tie them together with a few knots. Hide the ends inside the arm.
You can repeat all the steps for a better connection.
You will need to de extra stuffing to the body after you fix the arms. The better you stuff the body the less chances that your arm connection will loosen after a while.