If you freehand select anything on your canvas, the lasso tool will be your best friend.

How to Use the Lasso Tool

Tap on “Lasso” to freehand your selection.
Use your finger or an Apple Pencil to select the part of the image you want to edit.

Anti-aliasing

Toggling Anti-aliasing on or off to control what level of smoothing you want for resized areas.

Scaling

The scaling option allows you to resize the selection.

Selection Border

Tapping this allows you to add a border to the selected area.
From the drop-down menu you can select the border to be On Line, Inside, or Outside.

Flip

Tapping this inverts the selected area.

Copy and Paste

Tapping this copies and pastes the selected area to a new layer.

Release Selection

Tapping this resets the selected area.