One of the options children have been choosing to do is to create half or a quarter of a symmetrical shape / pattern. Then, they give it to a classmate to see if they can continue making the shape symmetrically.
Here is a design a student created and gave to a classmate:
Identifying the two lines of symmetry, the classmate was then able to complete the shape:
.....and what their classmate created:
Those choosing to do this during their wet weather indoor recess times have really been enjoying trying to create challenging shapes: