FeatureCAM can recognize only straight slots. They are recognized from straight, parallel side surfaces. You must select surfaces on both sides of the slot. In the example below, the shaded surfaces are the selected surfaces. The extent of the slot is defined by these surfaces. Note that the flat bottom surface is ignored.
For interrupted slots, select surfaces on each end. In the image below, the slot is interrupted, but can be created by selecting the wall surfaces at either end.
If the feature you are trying to recognize is a straight cut that extends off the side of the part, as in the yellow region of the part shown below, use a Side feature. You cannot recognize such a feature as a slot because it does not have opposing side walls.
You cannot recognize chamfers, draft angles, and bottom radii, but you can add these parameters to the slot in the Dimensions page of the New Feature wizard.