the Jesse tree can be an actual tree, usually with bare branches, not a Christmas tree, or it can be made on poster board or of fabric in a tree shape, any size.
the symbols are usually made like ordinary Christmas ornaments, but no glitter etc. there are several resources in printed books, most publishers of children’s RE materials have such a resource. Look in the black-line masters of your catechist guide, or on your publishers website link for catechists.
Each ornamant has a symbol of the OT figure in the stories that specifically pre-figure the coming of Christ, the Messiah.
examples
Adam and Eve - apple
Noah - ark or rainbow
Abraham - star or tent
Moses - 2 tablets
Jonah - whale
David - crown or star of David
John the Baptist - scallop shell (for baptizing)
and so forth
Our elementary CCD Advent retreat is based on the Jesse Tree. We have the actual tree in the sanctuary, and each Sunday Mass of Advent two of the children will bring up one symbol to hang on the tree, while one of the lectors reads the explanation of the symbol. This is at Father’s request, In past years we just did this in CCD.
The purpose is to teach the children about those OT figures and stories and how they relate to and foretell the coming of Christ.
They can make their own personal trees, just using brown marker to draw a bare tree on construction paper.
you could give them circles already cut out, or draw all the symbols on a piece of paper, and reproduce it for each student to color and cut out and glue on their tree.
If you are doing this, take the time to read of of the stories you are using from a good Children’s Bible.
some catechist magazines that have some good hands-on resources for the classroom are The Catechist and Religion Teacher’s Journal. each of them has had a recent article and how-to on the Jesse Tree.