This is the hardest part. It will probably take over 100 level 3 circles to get here. Eventually your guinea pig will expect a circle and be able to do them quickly.. When this happens you don't need to make your guinea pig follow your hand for a full circle, just put the treat either to the right or the left of their face (depending on the direction of the circle), say the magic words, and your guinea pig will begin to learn how to do circles without following the treat. Make sure to reward them for every circle. It is important that you never change the direction of the circle. When teaching your guinea pig to do a circle do not award a treat for a circle in the opposite direction you taught it (even though it is tempting at times) because this is rewarding them for not completing the trick correctly. After the circle is mastered, make sure to practice it often enough so that your guinea pig doesn't forget the trick.
Remember to be patient and have fun while teaching your guinea pig tricks! :)
*You can also teach this trick to your dog!https://www.instructables.com/files/deriv/F2H/3O6V/FJ0RH8NZ/F2H3O6VFJ0RH8NZ.MEDIUM.jpg