The Magpies had lost the services of goalkeeper Bartosz Bialkowski in the first-half when he was stretchered off after diving at the feet of Charlie MacDonald and taken to hospital after suffering a head injury.
Replacement, 19-year-old Fabian Speiss, proved an able deputy, pulling off a series of fine saves, but he was beaten twice in three minutes, first when David Mooney netted with a header and then Mathieu Baudry volleyed home from close range.
Although Jeff Hughes gave County a lifeline in the 77th minutes, the O's held out to claim their first win in five league matches.
"We earned that win and worked very, very hard to achieve it," Slade said. "All credit to their substitute keeper, who played superbly and to be honest, I didn't think we were going to beat him.
"He was saving everything, it was incredible, but once we did finally get the ball past him, it seemed to settle us down and we followed that up with a goal from a corner.
"There have been so many goals from corners and free-kicks in our games recently that you really have to be on your mettle.
"We got a great goal from Mathieu Baudry, it was a good finish because he's tucked the ball in with his left foot.
"It was our first league win of 2013, but we've deserved it. We've been playing really well, but just not been getting the result, although the lads' effort has been phenomenal.
"Both teams played some really good football and if you are a neutral, I think you have had your money's worth."