You can purchase lattice in the moulding department of lumber stores. It usually comes in a minimum of six-foot lengths.
Or you can buy a bundle of paint stirring sticks. Be sure to get the thicker, sturdier ones used to stir big buckets of paint. They are usually about 21" long. The small ones are too thin and flimsy for "Hammer Saw Drill" projects and many other project ideas. The dimensions you need for either the lattice or the paint sticks is about 1-1/8" wide and 1/4 thick.
Of course, you can always test out a thinner paint stick to see what happens and learn from experience. Educator and author Bev Bos said, "If it hasn't been in the hand and body, it can't be in the brain."
A figure made from a 1x3 and lattice, one of the projects
A six-foot piece of lattice moulding that has been cut in half
Heavy-duty paint sticks
So which do I buy, you ask? It depends on your preferences:
Lattice costs more, but is unmarked, a "blank canvas" for decorating later.
Paint sticks costs less (they may even be free in some stores) and usually have writing on one side. The writing can be painted over with acrylic paints, but not watercolor. It is translucent and the words will show through.
Buy only two sizes of wood. Build many projects.
Do you have a question about woodworking with children or people with disabilities?
Feel free to contact me.