Hold a tree or rock. Feel its texture. Look at its colours. Listen to its sound. Smell it. Let go of it.
Repeat all the above. Feel the tree with different parts of your body. Imagine you are the tree, and feel your solidity. Feel your roots going into the earth and your branches reaching to the sky. Feel the sap running in your cells, the wind in your leaves and the birds in your branches.
Feel your own body, and imagine the tree feeling you.
Hold the tree or rock.