How do spiders make long webs?

Yes some of them do make a silken ground-cover for the spot that they like to stand on while waiting for prey. They stand at the center of the (usually raised) spot where they like to stand and turn around and around while expelling silk in a broad band from their spinnerets. Then they keep extending the edges until they have enough covered to satisfy themselves.

Tarantulas that live in burrows will cover the walls of the burrow with webbing to improve their footing and to help prevent cave-ins. The method is the same.

Tarantulas that live in trees and bushes will make vertical silken "socks" to live in. The method is the same, but they start at the top and apply silk in a vertically hanging circle around themselves until they get the "sock" long enough to satisfy themselves.