The O's, currently in third place in League One, were comprehensively beaten 4-0 in Somerset as James Hayter scored either side of Joel Grant's goal before substitute Kieffer Moore completed the rout late on.
Slade said: "It was an unfortunate mistake from Jake in goal for the first and we rallied around at half-time and it was only 1-0 but the second was a bit of a killer really.
"The last one you can ignore because he is several yards offside but whether it is 3-0 or 4-0 they deserved to go through on the day.
"It is a difficult time for us because we have injuries and we are trying to bring one or two players in and still get results, so put this in a box and put it to one side.
"We're out of the FA Cup now so we can concentrate on the league and a very big game which we have on Tuesday."
- Sports & Recreation
- Joel Grant
- Kieffer Moore