Tuesday night's League One game at Brisbane Road took place in atrocious conditions of driving rain and a strong wind.
Both teams came close to breaking the deadlock, with O's 'keeper Jamie Jones denying Alan McCormack's long-range effort and Andy Williams hitting the crossbar, while Swindon stopper Wes Foderingham produced a splendid save to deny substitute Jimmy Smith.
"Nobody played for a draw and I thought that conditions were probably the winner in the end to be honest," said Slade.
"I thought that their 'keeper pulled off a really, really good save from our substitute Jimmy Smith right at the end to keep it at 0-0 because it was a really good opportunity.
"I thought they had the better of the first half and I thought we came more into it in the second period and looked a lot more of a threat. We played the conditions a lot better in the second half.
"There were one or two decisions that I felt didn't go our way. The referee overruled the linesman two or three times so yes, I did find it slightly frustrating.
"Swindon were denied by the woodwork but maybe we earned that little bit of luck. I asked the players for total commitment and that's what I got.
"We were up against a very good in-form side, who are a free-scoring side, and for us to keep a clean sheet in those conditions was excellent."