It's not too late to plant cucumbers, zucchini, and pumpkins. Amanda starts these in a pot because squirrels and rabbits like to dig up the seeds before they can sprout. Once sprouted, animals typically aren't interested in eating the seed. These plants do not like to be transplanted though, so the solution is to use biodegradable pots that can be planted directly in the ground.
You can make your own pots using newspaper using a paper pot press. There are several different sizes available on Amazon. The paper pots are easy to make and use, just make sure to put them on a non-perforated planting tray since they will be damp. Plant and sprout your seeds as usual. When you are ready to plant them in the ground, tear out the bottom of the pot so the roots can grow down into the regular soil without a barrier. The pots act as a short-term container of moisture until the paper composts and the roots get bigger.