Wilson won the World Championship in 2024 and was expected to go far in this year's UK Championship as the current world number two.
The two Englishmen played out a tight opening round with Slessor reaching a 4-2 lead before Wilson brought it back to 4-4.
Despite hitting 104 and 91 breaks in successive frames, the world number two was unable to go on and clinch the match, with Slessor taking the final two frames to book a spot in the quarter-finals.
"Where do I start?" Wilson asked TNT Sports.
"Just hard work. I wanted the ground to swallow me up. I didn't want to go back out after the interval.
"As soon as I missed the pink, I knew it was just un-doable for me. When you can't trust your equipment, when the table is so difficult.
"I just didn't want to be out there.
"I wanted to shake his (Slessor's) hand and walk out, but people pay good money to watch me play snooker. I battled, I gave it my all, but not to be."
Elsewhere in the evening session, Barry Hawkins secured a 6-4 win over David Lilley to advance to the next round.
He will face Slessor in the last eight on Thursday evening.