slow down!!

Just curious if its possible to stack slows? What i mean by that is, can you by a randuins, a frozen Mallet, and a Frozen heart, and maybe even slap someone with a fully stacked deadmans plate. And stop someone from pretty much moving or attacks for a couple seconds?

If i have a frozen heart (slows enemy attack 15%) and then hit them with a Frozen Mallet (40% moevements speed decreased for 1.5sec) now has them unable to run away or hit me. But then if i have a randuins omen. When hit by a basic attack it reduces attack speed by 15%. Is that 15% on top of the 15% already being used by frozen heart, or does one cancel the other? Plus, what if i activite my Randuins in the process and slow their movement speed. Does that Stack with Mallet, or does one cancel the other?

Of course there are others like iceborn gauntlets, rylais, and Deadmans plate. But i assume you will tell me they cancel each other. But the 'unique passive/active' for each has a different way in which it activates so i didn't know if that meant it could stack or not.