I have been struggling to describe in writing how I achieved this so bear with me.
What I did first was create the outer rectangle, but leave it Square (ie dont apply the fillet yet). Next create the Inner rectangle and make sure you place its center point at the same location as the outer rectangle. Now depending on how much space you want between the inner and outer feature adjust the dimensions of the inner rectangle accordingly (ie if you want a 1/4" offset make the rectangle 1/2" smaller in height and width).
Now create a circle with the radius you want for the “bump”. Dont worry about placing it yet.
Now click on the Inner Rectangle and select the Upper Left dot on the MOVE panel. Make note of the X and Y dimensions. Now click on the circle you created and enter in the previously noted X and Y dimensions. If done correctly the center point of the circle should lie on the upper left corner of the inner rectangle.
Now repeat that 3 more times. Create the circle and set the radius. Click the inner rectangle and choose the corner point in the MOVE area you wish to use, note the dimensions, click the circle, and enter those dimensions into X and Y.
When you are done it should look like the attached photo.
The final steps are select the Inner Rectangle and one of the circle and choose Boolean Subtraction. Repeat always making sure to select the Inner Rectangle first.
Last step is the Fillet. Choose the Outer Rectangle and instead of Square choose Fillet and set your radius.
Good luck and feel free to message me if you have any questions