When you burn a layer of enamel on the surface and do not add granules, threads, cloisonne wire or other things, then usual it is not necessary to apply counter enamel to the backside. You can clean the backside with a sanding block or whatever you use to clean, and the enamel job is done!
If you like to give a luxury appearance to your art piece then you can give it a treatment with the silver plater.

Most of the times, unfortunately, you will discover that your art piece needs to have a layer of counter enamel at the backside.
Expansion in the materials (on the glass and the material it is applied), will cause cracks in the surface of the glass. Sometimes it can have such a strenght that the glass pops of.

Myself I use leftovers from enamel sessions.
To start with your own stock of counter enamel, simply take a little scoop of all the colors you have and put them in a container and shake well.
Congratulations, you have made your own stock of counter enamel.
If you add some more black enamel to it, then you will get a nice dark counter enamel color.
All these colors makes together a balanced counter enamel with just the right expansion

COUNTER ENAMEL RACKS

When the backside is done with the counter enamel, then the front side needs to be done.
To do this the art piece must be situated on something, in such a way, that the backside is not disturbed while burning.
Obviously it cannot be done while resting on a regular firing rack, the enamel art piece will sink into the raster of the rack and it is almost impossible to get it of.
Besides, the backside will be ugly.
There are several commercial counter enamel firing racks available. 

Ceramic stand	Ceramic rack On your left you see a standard made of ceramic. The principle is that it has to have some sharp points and edges where the art piece can be situated while burning. On this way you can, when it comes out the kiln, lift it from the firing rack. Disadvantage, it will leave behind ceramic leftovers at your art piece So I have made my own counter firing racks

Custom made firing racks.

Small and big pieces	Big Pieces	Small pieces

Herewith a few firing racks I modified myself.
I use pliers, like below, to get the art piece from the sharp points of the screws
The sharp edges on the backside caused by removing the art piece from the rack, can be removed with tweezers or a sandingstone.

The first rack I made for tiny pieces
I fastened the long screws with some copper wire.
On this way it is possible to let rest the tiny pieces on the sharp edges of the screws.

I have made the model into the middle to work with little and middle size pieces.
Take corrosion resistant steel screws and fasten them with nuts.
You need to use some force in the beginning to accomplish this, however when this is done you have firing racks with a lifetime durability.
The sharp points of the screws do not left any marks on the backside of the art piece.

The model on the right is made like the middle one, however the distance between the screw is somewhat bigger.
On the picture with the advertisement for workshop you can see how I use it to handle a art piece into the kiln.

Pickup the artpiece	Lift the art piece of the firing rack. When the art piece comes out of the kiln, it has to be cool down on another flat surface. After the glass is hardened you can pick it up like you see on the left. Careful now ! It will easily be damaged. Pick it up and you will see that the backside is almost not damaged.