Shape Challenge - pebble, stick and rectangle

I've used found objects as a starting point for these sketches.

A friend set the challenge above which was a small stick.

The one below was rectangular shape with a corner, cannot remember exactly what.

I did these a while ago, but now I try to remember to draw around the item as a reference, like in the flower picture below.

another one set by a friend, this time a pebble

I created both of these using the pebble.