First off, i make a simple box

Then i added subdivisions to the box.

Change to Vertex Mode

And moved the intersecting vertex close to the sides of the box

Next i extruded the top face of the box downwards, that will make a cavity that will really make it look like a box.

There you go.

Next I selected the top side faces of the box and extruded it out to create the flaps.

I used the rotate tool and placed the pivot downwards so it looks like the flaps are opening up.

next i choose the edge loop tool and applied the loops accordingly 

and i selected the vertex at the flaps and used the move tool to move the vertex out of place

I beveled and Smoothen it.

Voila!

The torn box was made from scratch and separated one of the flaps. so i can easily manipulate the flap.

Because the flap is not connected to the rest of the box, i can easily rotate the box to the desired angles

Reflections: the box extruding the faces is easy but when it comes to rotating the flaps, i remembered my first time, i got very frustrated. but as i keep on doing it over and over again, it gets easy