Steps 1, 2 and 3 - run around town to thrift shops and buy as many cool shoes as possible - size doesn't matter since I'll never wear them - drill drainage and hanging holes; water proof shoes.
Step 4 - hang them from the tree branches
Step 5 - explain to the neighbors what a shoe tree is - then enjoy the yard art!
Keeping my fingers crossed that neighborhood kids don't steal/"borrow" the shoes!