Shape Sorter too Challenging?

So many of the shape sorters that are available commercially are too challenging for toddlers when they start with this type of activity, as there are too many possible holes that each shape can go into. This can lead to lots of frustration and avoidance of this type of activity in the future. Making a shape sorter out of a yoghurt container that only has two options is a great way to start. This child is sorting according to SIZE, so she is using milk lids and cold drink lids. We have another set of lids that have a square and a circle cut out, and another set with a square and a triangle, etc. Once the child understands the concept, then he can move onto the shape sorters with lots of shapes and achieve mastery relatively quickly.