You can select several faces to define a normal sheet metal side wall not top or bottom faces.
Flattening sheet metal solidworks with cuts.
Your best bet would be to make this using the sheet metal functions unfold it add your holes fold it then if you need a surface to do a surface offset of 0.
To flatten the entire part if the flat pattern1 feature is present unsuppress flat pattern1 or click flatten on the sheet metal toolbar.
In the featuremanager design tree select the part and click flatten sheet metal toolbar.
In the cut list right click the body and click flatten.
With the normal cut tool you can normalize all non normal side walls in sheet metal models.
To flatten a body do one.
In either the featuremanager design tree or the cut list right click the flat pattern feature for the part and click unsuppress.
These improvements also provide better flattened geometry for certain corner treatments lofted bends and in some cases where cuts intersect bend regions.
In addition a cut list contains a separate representation for each body with a flat pattern specific to the body.
To hide the bend lines expand flat pattern1 right click bend lines and select hide.
The bend lines are shown by default when you unsuppress flat pattern1.
Improvements to flattening sheet metal parts make flattening succeed for complex shapes which previously failed.
Multibody sheet metal cut lists offer the same features as weldment cut lists including the ability to automatically organize and update sheet metal bodies and view sheet metal properties.