I saw a similar pattern by Sarah London. You can find it online. This pattern and photos shown are only a three layer tree. You can make two to seven granny squares. Always edge last round with alternate color.

Assembly bits shown: Two round square, turn & pull up one edge to center. Tack. Three round square, repeat. Four round square. Repeat. Start with largest square, put next smaller size on top (I usually put bottom edge at point of larger round) Repeat each layer & tack or glue all together. Decorate as desired. Green yarn ~ homespun by Lion, Red yarn Charisma from Michaels store.

Last photo shows a three layer tree which is about 12” tall, time required about an hour. You can add
a trunk if desired, make into a mug cozy, hang on wall or whatever suits you.