I would create a poly plane, then Edit Polygons, Duplicate Face (separate faces selected in the option menu), adjust with and height for the hole, duplicate the face (ctrl d) for the second hole, combine all and use the 'make hole' tool; then extrude the face to desired depth...
...well if I just think about it... maybe you'd better go with 'booleaning' cube and cylinder (worked to much with polys lately)