Forest Road 307, Grand Canyon NP
Forest Road 307 might place you furthest away from Grand Canyon's visitor center and main attractions, but it offers some amazing boondocking sites with gorgeous views of the desert landscape. The best sites are within the first two miles from its entrance from Highway 64.
Old AZ 64, Grand Canyon NP
Old AZ 64 (appears on Google Maps as "64A") offers dispersed camping opportunities for those wanting to explore the attractions and trails in the eastern part of Grand Canyon National Park. There are about a dozen or so previously-used campsites along Old AZ 64 and Forest Road 6104.
West Side Highway 67, Grand Canyon NP
The east side of Highway 67 along the North Rim of Grand Canyon National Park has more forest roads and more camping opportunities than the west side. Served by Forest Roads 22, 270, 222, 1046, 1047, 1048, 1049, 1050... This is where most dispersed campers go to find free camping.
East Side Highway 67, Grand Canyon NP
The west side of Highway 67 takes Forest Road 611 to several other forest roads (610, 216, 2650, et al). Dispersed camping is allowed all throughout these roads. It's recommended you download the Motor Vehicle Use Map (see Downloads below) and keep it on your phone for later reference.
Saddle Mountain Overlook, Grand Canyon NP
Probably offering the most spectacular views of the North Rim, Saddle Mountain Overlook has only a few previously-used places to camp, although dispersed camping is technically allowed anywhere as long you don't drive beyond 30 feet from the side of a road.
Forest Road 310, Grand Canyon NP
Also known as "Coconino Rim Road", the first mile of this road starting from Highway 64 is off limits to camping due to being within a one mile radius from Hull Cabin (see rule in Downloads below). You generally have to get south of the intersection with Forest Road 307 before getting to the dispersed camping area.
Long Jim Loop, Grand Canyon NP
Long Jim Loop is a 3/4 mile dirt road encircling the northwest portion of Tusayan Village. It's a forest road open to dispersed camping. There are about a couple dozen previously-used sites here. The forest's policy of remaining within 30 feet from the side of the road still applies here.
Forest Road 302, Grand Canyon NP
Forest Road 302 starts at Highway 64 inside the town of Tusayan and heads east. Historically, the first 1/4 mile of this road was off-limits to camping, but it seems these days there are often people still camping within this restriction. Still, even when you get past the 1/4 point, there are dozens of previously-used sites to choose from.
Forest Road 688, Grand Canyon NP
Forest Road 688 heads east from Highway 64. The first mile of this road is off-limits to camping because it is within one mile of a developed campground (10X Campground). But when you get past that range, there are dozens of previously-used campsite, as well as dozens more along spur roads branching from it.
Forest Road 305, Grand Canyon NP
The first mile of Forest Road 305 has dozens of previously-used dispersed campsites, as well as dozens more along spur roads leading off from it. The road itself is firm packed dirt suitable for any vehicle or RV, but don't stray too far off road as the dirt gets soft.