Rectangle with scalloped corners

I'm trying to make a rectangle with scalloped corners. I draw the rectangle then I draw 4 circles and place each circle on each of the four corners of the rectangle, then Arrange|Combine|Slice.

3 questions:

How do I snap the centre of the circles to the rectangle's corners points (clicking on the Snap to Object icon doesn't seem to highlight the circles centre point)?

When I select all 5 objects and Arrange|Combine|Slice only one of the 4 circles slices one rectangle corner -- i.e. not all 4 as I expected -- and the remaining interior arc has to be deleted manually?

Is there perhaps a hidden keyboard combination that can be used with the rounded coners option of the rectangle toolthat will scallop the corners to a set radius (ideal solution)?

Thanks

I'm not sure if the circle centres will snap (maybe someone else can answer that one). What I do is align the selection bounds handles as in the pic below. If you then group the 4 circles, select the group and the rectangle, then Arrange|Combine|Subtract, you'll find that you can do it in one go.

Make sure snap to objects is selected and the circle has not been converted to an editable shape.

"Grab" the circle near its center and drag it close to the corner of the rectangle. It will snap in place.

Before subtracting the circles from the rectangle, either group them or join them.

Here's another possibility -not sure if it saves much time though...

Carygee's idea of being able to enter negative (therefore scalloped) rounded corners seems a good suggestion for an improvement.

Tony