Coventry started the season with a 10-point penalty after administration, but Steven Pressley's men beat the leaders 3-1 as the sides met for the third time this season.
Orient missed a first-half penalty but were soundly beaten and only managed a consolation in second-half injury time.
And Slade reckons the Sky Blues, who are playing 35 miles from home at Northampton, can keep their form going.
He said: "This was going to happen at some stage this season but I was really pleased with the attitude we showed, even at 3-0.
"It is fine margins. I am not saying that we deserved to win because we didn't, but maybe if we had taken the penalty it could have changed the game.
"We were not having a great night but if we had scored and started to come back they might have begun to wonder. But we didn't and they scored five minutes later.
"Their first two goals were very well worked. I have had a good look at Coventry and if they stay injury free they can get in the play-offs because they are a really good outfit and they have got real momentum."
Coventry skipper Carl Baker cracked in the first goal in only the 10th minute when he rifled in a left-foot effort from 25 yards.
At that stage the home side were firmly in charge and had adapted better to the awful conditions.
Baker could have added a second and Callum Wilson also saw a shot blocked.
But after surviving two scares just after the break, Orient looked to have earned their way back into the game in the 57th minute when Jordan Clarke fouled Shaun Batt in the area and the referee awarded penalty.
David Mooney struck the spot-kick low and well but Joe Murphy read his intentions and saved down to his right.
Orient's chances disappeared with that save and Franck Moussa scored with an audacious chip in the 66th minute before Leon Clarke bagged a header in the 76th minute.
Substitute Yohann Lasiment scored a late consolation for Orient.