How about uploading your SKP file so we can see exactly what you’re working with?
Two common scenarios:
1.You have made a component or group of the table top and you don’t have it open for editing before you draw the rectangle for the cut out. If this is the reason, open the component/group for editing before trying to draw the rectangle.
2. You aren’t drawing all of the edges for the cut out on the face of the table top. If this is the reason, make sure you are getting On Face messages when drawing the edges with the Line tool.
If the perimeter frame os going to be the same width all the way around, you might use the Offset tool to create the inner rectangle. It would be fewer steps and wouldn’t require any layout.