To make a homemade minion costume, wrap a foam pad in a cylinder around the costume wearer to measure width. Cut the pad to the width measured with the length of the pad measuring from the upper hips to 1.5 feet longer than the head.
Cut petal shapes 6 inches long into the top of the pad. Hot glue the petals together using a kid's size bicycle helmet as a guide until all the petals are glued into a dome with a star-shaped hole in the center. Glue a piece of foam under the petals to hold them in place and glue 5 inches of the seam to avoid pulling. Create a paper template for the eyes and mouth and pin them to the head to get a good proportion.
Trace the mouth using the template, cut it out and add extra foam for the bottom lip. Add padding from the top of the dome to above the mouth and cut arm holes in the appropriate place. Use yellow spray paint to paint the base of the minion. Cut teeth from extra foam and glue them inside the mouth.
Create goggles by contouring an instant oats-shaped can to the head. Wrap and frame the front of the container in silver paper. Use leftover foam for the eyes with brown and black foam as the iris and pupil and glue inside the goggles. Glue a black fabric strap around the head and glue the goggles over the strap. Glue a circle of matching yellow felt with black pipe cleaner hair to the dome.