Yes, overall you can boondock just about anyplace in Alaska, but stop and think about in Anchorage. RV parks are very limited and very small. There's the:
Golden Nugget on Debarr across from Costco
Centennial Campround owned by the city for small rigs and tents
Midtown RV Park on Northern Lights which is very small
Anchorage Ship creek RV Park, newer but a little crowded
Creekwood Inn & RV Park - old & on it's last leg
Black Spruce - Military only
Considering as many RVs that come to town every summer, there's really very few spots for them.
Yes, again, there's lots of boondocking room around Alaska, you just won't find anything around Anchorage. On the north side of town you have to boondock out 50 miles to someplace north of Wasilla or Palmer.
On the south end you'll have to go about 50 miles also to the road going to Portage Glacier or into the RR parking area. They might let you stay one night, but then I'm sure the guards will ask you to leave. So there's not a lot of options in Anchorage.
Bill