If you wanted your quilt to have a "checkerboard: effect, could you include the precut plain/patterned squares for in between the squares the next person would do? For instance, if you had a flowered/striped/checked or whatever theme fabric, could you include say three plain squares for that row and the next person would do four squares then four plain for the next row and the person would do three squares for that row...hope this is clear lol I am not sure what you mean by adding sashing for the person...that may be beyond me.
Margie