Ashton scored twice in the comfortable victory, which helped the Saracens book their spot in the quarter-finals of the competition.
"It was great to see Ashy score a couple of tries and getting back to what he really does best. The second try was fantastic and I wish I could claim credit for thinking that up; Ashy and Owen (Farrell) just saw each other and they pulled it off," Ashton told reporters.
"We can appreciate just how difficult it was out there and we said after the game that the conditions were as bad as it gets with the ball like a bar of soap.
"The key was being patient and to keep our composure, but also to control the game enough through position and with that the opportunities would come and then we would put them away."
The victory ensured that Saracens finished top of pool one.