Directly from the help file:
To create a part of uniform thickness and convert it to sheet metal:
Create a block with the Base-Extrude tool. Make the block 50mm on all
Shell the block to 1mm so the part is of uniform thickness. In Faces to
Remove, select the faces as shown.
To bend the part, rip the block between the edges of the tabs by
clicking Rip or Insert, Sheet Metal, Rip. Select the edge to rip as
Convert the part to sheet metal by clicking
Insert Bends or Insert, Sheet Metal, Bends.
If you want to make a cut across a bend, drag the Rollback Bar before
the Process-Bends feature in the FeatureManager design tree.
Sketch a closed profile across one of the bends.
Extrude the cut Through All.
To restore the part to the bent state, drag the rollback bar to the
bottom of the FeatureManager design tree.