The Arsenal captain was named in the 23-player group for Canada 2015, which will be her third experience of the tournament, following her most anxious wait yet.
Scott said: "People kept telling me I was nailed on for selection. They couldn't understand how nervous I was.
World Cup fixtures
v France, Tuesday 9 June
v Mexico, Saturday 13 June
v Colombia, Wednesday 17 June
"I think it was the most nervous I've ever been. The competition for places is better than ever. I know how hard I've worked and I know how hard everyone else has worked too.
"There was never a time when I thought I was guaranteed my place."
The phone call from her head coach came on bank holiday Monday.
"I didn't leave the house," Scott said. "I was scared of missing the call. I didn't even walk my dog.
"I cut my grass, did some washing – anything to take my mind off it.
"When Mark told me I was in, it was a huge relief. But the real hard work starts now."
England begin their campaign against France on Tuesday 9 June, followed by matches against Mexico and Colombia.
Sampson has selected eight World Cup debutants alongside seven players, including Scott, who will be playing in the showpiece event for the third time.
Scott added: "I'm sure it was really tough for Mark to pick just 23 players, but looking at it, I think it's a really exciting squad.
"The squad announcement was the biggest media turnout I've seen out of the three I've been a part of so that just tells you everything you need to know.
"All eyes are on this World Cup. It's going to be the biggest one yet."