Jean-Philippe Mateta and an own goal from Nathan Collins saw Palace win 2-0 at Selhurst Park.
"I told everyone in the pre-match press conference that they scored two and we scored two from long throw-ins," he said. "To be honest we didn't have too much time to work on the the training pitch.
"Thursday was recovery and then yesterday we trained 25 minutes on the pitch, then 15 minutes on throw-ins, both defending and attacking.
"We knew this would be a topic today. So credit to my assistants who prepared all the clips and the set-up.
"We spoke about it and said it could be a ‘set-play battle.’ And I think in the end we won the set-play battle. We scored two goals and that's why we could win the game.
"It's a very, very important and good win today."
Glasner added: "Set-pieces have always played a crucial part. We'll always have a focus on this.
"In tight games, it can help you win games. Today it helped us, that's why we're all pleased and delighted now and can have a good evening.
"We didn't expect an own goal, but both teams have tall players. We know when we get the ball in the right areas, anything can happen."