Building a model of a California mission is a popular school project for Californian fourth graders. While companies have capitalized on this and created ready-made mission-building kits, building your own from scratch can be a fun and rewarding experience and will create a more unique result. Use cardboard as a base for building your mission model.
Cut two pairs of rectangles from a cardboard box, all four the same height and one pair longer than the other, to serve as walls for the mission. Cut archways into the longer pairs by cutting away upside-down letter "U" shapes from the bottom, longer edges of the rectangles.
Glue the walls to the cardboard plant tray with hot glue, arranging so that the pairs of equal length are opposite each other to create a rectangular box with no lid. Be sure the longer sides are facing the correct way so the cutouts look like archways. Glue the sides of the walls to each other to hold in place.
Cut another rectangle from the cardboard box. The rectangle should be a few inches longer and wider than the rectangular missing top "side" of the rectangular box of the glued walls.
Rip the top, thin layer of paper from the cardboard rectangle to expose the rippled layer of cardboard beneath. Fold this rectangle in half lengthwise with the rippled layer on the outside. Crease and unfold. This will serve as the roof. Glue the roof in place over the walls by applying hot glue along the top edge of the walls.
Mix red, brown and white acrylic paints on a paper plate to create the desired hue of your mission's wall and roof colors. Paint desired color onto the cardboard walls and roof.
Decorate the empty space in the tray around your mission by designing a mission garden. Use faux moss and small artificial flowers from a craft store, and make paths through the garden with sand and pebbles.