In a bowl, mix the flour, salt, and warm water. Knead it with your hand until all combined. (If it's too sticky, add more flour a tsp at a time. If it's too dry, add a tsp of water at a time and mix.)
Use a rolling pin and roll it out flat.
Use a tree cookie cutter and press it into the dough. Cut a star using a tiny cookie cutter or make a star shape out of cardboard for tracing the star toppers.
Have the kids press their fingerprints on the tree. Poke a hole on top of the tree and star with a pencil or straw. Make sure you smooth out the edges because they will dry jagged if you leave it.
Bake at 250 degrees for 3 hours, flipping halfway.
Let them cool for a few hours then use acrylic paint for the star. Have the kids dip their finger on an ink pad and press it into the indents they made.
Use the sharpie and draw string lines between all the fingerprint lights.
Write the year or name and seal with mod podge. Tie a ribbon and you're done!