Flat 8/2W/GND UF Wire

You cannot just lay it on the ground.

You can run it up off of the ground under the floor joists. If you attach it to the sub-floor, you must have steel plates to protect it from nails coming through the floor (regardless of whether or not you THINK it will happen). What most people do is to drill holes in the joists and string it through the holes for perpendicular runs, along the sides of the joists at about mid-height for parallel runs. An alternative is to nail a "running board" to the joists and strap the cable to the running board. Sometimes in a limited work space like that it is easier that way; trying to drive stapes into the sides of joists or drilling a lot of holes in the spaces between them while laying on your back in the dirt (with Black Widow spiders crawling around in Central Calif.) is not fun.

By the way, it doesn't need to be UF if it is not buried in the ground or exposed to the sun. Regular NM cable would suffice. A crawl space is considered a protected area.

PS: rodents seem to love chewing on plastic cables. Armored cable would be a better idea if it is going to have any exposure to being accessed by rodents.