Browse photographs of the Santa Cruz mission online. Be sure to do an image search through an engine such as Google, and also visit the mission's official website through the California government homepage.
Sketch on a piece of paper what you want your mission to look like. Work with any class instructions or guidelines received from your teacher. Make a list of any supplies you need and shop for these at your local craft and grocery stores.
Draw placement lines on your base (plywood or cardboard). Be sure to include outlines for church walls, corridors, gardens, bell towers, etc. Any ground-level feature of your mission should be provided with these placement lines.
Construct your walls out of your preferred material so they are at least three inches tall. You may use sugar cubes, clay, dry pasta, or anything else you can think of. Generally, there are no strict guidelines on material used, so feel free to be creative. Salt dough is often another popular choice, and the recipe can be found in the References section of this article.
Make your roof out of dry pasta glued to cardboard, and then paint it your desired color, such as a brown-red that is often seen on actual California missions. You can also opt to leave your mission roofless and add detail inside, such as clergy figurines or furniture.