Adding holes simultaneously within mesh Im trying to add multiple holes within my mesh, so I divided it up, and then used cylinders shapes to make the holes. On the top image I used the Boolean operation.
And on the bottom image, I subdivided one of the rectangles and used the looptool method with the circle. Once I add a subdivision modifier I am getting weird result with the Boolean but the operation holes, but the bottom Hole looks more acceptable once cleaned up. Is one or the other method the correct way?
Select the face you want holes on
Inset all faces by pressing "i" 
Extrude all faces by pressing "e"
Extrude all faces by pressing "e", press "g" and drag them down 
Extrude all faces by pressing "e"


(3. and 5. sharpen the edges, so you don't have to add Loopcuts/Edge Creases)