depends where you live.
if you live in the snow belt and will be bringing in vehicles full of snow and snowmobiles etc. like i do you will have water problems. Where i am from if you are smart you put a concrete pinned curb atop the slab and stick frame above the curb. In my case I have a 8" wide and 8" tall curb all the way around my garage slab and the bottom 2x6 sill is anchored direct into the curb.
If you arent to far into the framing and this is a concern to you i would put a concrete curb on your slab.
Probably too late for a curb. Only a sloped slab or a really good crew would eliminate all low spots and puddling. A curb just keeps the framing dry, but you've used pt on the plate anyway so unless it's constantly saturated you're OK.
Once the roof is on most of the puddling will be forgotten. Rain leaves more water on the slab than you'll get from snow melt, but I'd keep a squeegee on hand.
Maybe too late for a concrete curb but the framing could be unbolted from the slab and a course of block put down. That would prevent further issues with water and the framing.
I'd be curious to see the rest of the build and if an apron, porch or sidewalk was poured at the same time as the garage floor.
