Maxi Duna Multy is 100cm by 51.5 cm
I also recommend the Kallax unit - I have had a 100cm by 54cm cage on top of that with no problem.
Maxi Duna Multy
https://www.amazon.co.uk/Ferplast-Ma...axi+duna+multy
Kallax unit (various colours)
https://www.ikea.com/gb/en/products/...-art-70307493/
The Fjalbo you linked isn't deep enough to support a cage really(it's only 35cm deep). The other thing is - if it's a top opening cage like the Ferplast Duna's you don't want it any higher up than the height of the Kallax unit (and lower than that is better really) or it's awkward doing anything inside the cage or having interaction with the hamster.
I actually think the ideal height for a cage is on something like the Lack Coffee tables. Our 100 x 54cm cage is currently on top of something the height of a coffee table and it's much more manageable. But if you want shelving, the Kallax is fine.