Assemble Ikea Ringhult back/side panels

Hello dear ones,
I am brand new here and I hope you can help me.

I am currently setting up a new METOD kitchen. Everything worked great, but now I am a bit stuck.
Here is the problem: I have a small freestanding kitchen island - consisting of 2 small cabinets (left and right) and a 60 cm cabinet for the stove in the middle. Now I have received Ringhult side panels for this island. Attaching them on the sides is quite easy - just screw in from the inside, done. BUT: how do I do it on the backs of these 3 cabinets? I can’t just attach the side panels to the flimsy backs - meaning the bulky thin back walls (I hope you know what I mean). Somehow I am having a blackout right now and can’t figure it out.
Can you help me? *looking at you very kindly*
Best regards

I believe you don't have a blackout, I think the side panels are not intended for the back panel at all. Without aids, e.g. small brackets, it is probably not feasible.

Exactly, you still need craft materials (Eisenwinkel) from the hardware store and will probably have to saw the cover panels to size (or have them sawed).

Hm - that's obviously not so great! :/ Especially since I had the kitchen checked at Ikea (which I actually think is a great service). Ok, then I'll try using brackets tomorrow - somehow we'll manage to secure the parts. Many thanks for your answers and all the best.