XCrysDen is a very easy and nice program to see the ELFCAR, first you have to convert the ELFCAR to ELFCAR.xsf with the v2xsf script from Jens Kunstmann (http://theory.chm.tu-dresden.de/~jk/software.html), after that is pretty easy to use it to see the information from ELFCAR. Attached is a picture from a 2d slice of graphene layer with OH units. If you wish a figure for a paper the best option is to use VESTA, but, if you just want to see the results is easiest and faster to use xcrysden.
Open the cube file using vesta and you will see iso-surface, and in utilities go through 2D data display and click on the slice there you will find hkl plane select it along with the distance from the origin and apply. You will see the 2D slice in any plane you want and from any distance from origin.