Slimmest is the correct spelling.
The M is doubled before adding the -EST.The correct spelling is slimmest.e.g. She was aiming to be the slimmest person on the dance team.
The superlative form of "slim" is "slimmest."
slim, slimmer, slimmest
I won the footrace by the slimmest margin. Only the slimmest fish could escape the mesh of the net.
I have tried slimmest and don't like itI have tried slimmest and its to sweet and l don't like it,
slimmer, slimmest
Samsung U-100 is the slimmest mobile phone. With its 5.9mm it is 1.0mm more slim than its predecesor the Samsung x820.
Sony's DSC-T7
33/50 = 0.66
if you have polio they are thin or you can shave them
The superlative of slim is slimmest.
Maybe a Line 6 variax acoustic.