installing a vanity unit with sink! Help

[vik2001]

im installing a vanity unit in the bathroom. when i put the cupboard unit against the wall its not flush. my floor has a dip in it.
the vanity unity touches the wall along the bottom, then as it goes up theres about a 20mm gap away frm the wall.
i cant scribe it onto the wall as its fixed, is my only option to pack it out at the bottom?

 

[bathstyle]

Scribe the bottom?

 

[IJWS15]

Don'tassume the floor is level or the wall is vertical.

Pack the unit so it is level and see how it fits the wall/floor then.