I am making a pea gravel path that is on a slope and want a plant that will hold the gravel and prevent it from flowing down the slope over time. A few details
Northern Colorado Zone 5b
I am putting sand in with the rock but no soil
This is by a driveway so it will rarely be walked on but cannot be slippery in ice.
OK so what are my options
I usually see ornamental grasses in rock gardens, but it sounds like you want something you can walk on? There aren’t good low ground covers I know of for rock gardens in your zone. Maybe look at wineleaf cinquefoil, which stays pretty short and could be occasionally stepped on.
I’m not sure what you mean by it can’t be slippery in ice. Most plants are going to be slippery if they get covered in ice.
I live in south Texas and so no ice here.
We have found that if you put good quality landscape fabric before putting in the pebbles, they don’t get washed down.
Not sure about plants in your region
I’m having trouble getting past the concept of a pathway that will rarely be walked on. 
What might work better in your situation than trying to root plants into sand and pea gravel (while competing with weeds) are stepping stones or steps, softened by low-growing plants.
It’s an 11 inch “path” so the landscaping doesn’t abut directly to the driveway. Since it is next to the driveway it’s possible that someone will step on it getting out of the car but it is not a path like “let’s take a stroll”