It will not appear under this circumstance. One solution, if your shape has curves, is to draw the shape you need to subtract with the Polyline Tool, select the slab, bring up the Pet Palette and select the Subtract from Polygon option, then Magic Wand the Polyline shape.
David
David Maudlin / Architect www.davidmaudlin.com Digital Architecture AC27 USA • iMac 27" 4.0GHz Quad-core i7 OSX11 | 24 gb ram • MacBook Pro M3 Pro | 36 gb ram OSX14