For a canister filter, usually you don't hang it at the back unless it's a very small canister.
They might be too heavy for you to hang at the back unless you are sure that your tank is strong enough to withstand the weight.
If your tank has a frame, then it might be ok to hang it.
For a frameless tank, there is a risk if the filter is too heavy.
Usually you put it under the tank(for two tiers stand), or inside the cabinet or on the floor.
If your table/cabinet is wide enough, then you can put it at the side (left or right).
I attached a photo of how it looked like if you were to put it at the side of the table, provided your table still have space at the side.
I guess some of the smallest canisters are
Shiruba XB-305, Eheim Classic 150 or Oase 100.
I like Oase 100 flow rate as it's more powerful and better than Eheim and Shiruba.
It's also easier to clean as the filter pads/medias are not stack on top of one another.
The filter medias are put side by side making them easier to take out for cleaning.
You can check the dimensions from the websites below:
The FiltoSmart 100 external filter has a compact design with a large filter surface, perfect for marine and freshwater aquariums. Utilizing biological and mechanical filtration, this external filter, ensures effective water filtration and optimal living conditions for aquarium inhabitants.
store.oase-usa.com
*This item is qualified for FREE SHIPPING to all 48 continental states! Additional shipping fees may apply for shipping to Puerto Rico, Hawaii, and Alaska. 1. It can be used as a hang-on or external canister.Large filter box, additional with multiple filter materials.Separate inlet & outlet...
aquaforestaquarium.com
www.eheim.com