When you place a 35 slots bag in an other 35 slot bag, it takes 25 slots.
So you can put a full 35 slots bag in an other, and have 10 slots more for other items.
So you can repeat that and have infinite slots.
And it's the same for some clothes, which take 6 slots in a bag, but contains 8 slots. So you can combine all that to have infinite slots.