Choose a pumpkin for your flower arrangement. The pumpkin should have a flat bottom so it won't tilt or lean. It should be fresh with no soft spots. Consider what kinds of flowers you will be using and coordinate with the colors of the pumpkin.

Place bowl on the top of your pumpkin and trace around it lightly with a sharp knife. Set your bowl aside.

Using a sharp knife, cut all the way through the skin and meat of the pumpkin into the hollow center, following the line you traced around your bowl. Pull your top completely out and set it aside.

Using a spoon, scoop out the pulp and seeds. Discard or save the seeds to bake for a snack! The sharp edge of a spoon helps to get all of the pulp out.

It might take a few extra little shavings with your knife here and there to fit your bowl into the middle of the pumpkin. Once it fits snugly into the middle, fill your bowl with cool water. Add a flower frog or tape a grid to the glass using floral tape. 

Start with a few branches of fall leaves around the base of the arrangement. Add some sturdy flowers in a rough globe shape, creating the structure of your pumpkin flower arrangement. I used dahlias and mums for this step. Fill in the holes with other filler flowers. I used kangaroo paw, hypericum, and stock for this step. Fill in any extra holes with more fall leaves. Check to make sure it feels like it all flows evenly and make any needed adjustments.