Learn how to remove faces from the geometry:
Launch either of the Simplify or Edit Model contextual environments:
In the Simulation workspace, on the Setup tab, click Simplify > Simplify .
The Simplify contextual environment opens.
In the Generative Design workspace, on the Define tab, click Edit Model > Edit Model .
The Edit Model contextual environment opens.
Click Modify > Remove Faces .
On the canvas, select a face or faces that you would like to remove.
In the Remove Faces dialog, click Delete .
Optionally, press Esc to cancel a long-running Remove Faces operation while it is in progress. The geometry will revert to the prior state.