It can be 2-dimensional or 3-dimensional. Be as open-ended as you want. Some kids prefer a little structure (how could we use these to build a robot/rocket ship etc.), and some just want to grab and go, letting their imaginations run wild.
It’s fun to use a mix of mini- and large marshmallows. Colored toothpicks also add some zest. We like to build on plastic trays or cardboard flats (the better to transport with). Be sure to take some pics before the creations become snack-time confections!