A victory of any sorts against such star-studded opposition and on French soil would have most teams wearing an extended smile yet Leinster know improvements will have to be made when they face Ulster in the tournament's showpiece on May 19.
"Of course we're delighted to have won the semi-final but we haven't really achieved anything yet," said Boss, who started the nail-biting 19-15 win in Bordeaux ahead of rival No9 Eoin Reddan.
"There was probably a bit of relief at the end there. We held out well and showed a lot of character but there were lots of parts of our game where we were a bit scrappy.
"Our setpiece wasn't as strong as it could have been in the first half and we lacked a bit of momentum through that. That was there for us all to see and it's there for us to fix.
"They were very physical, they managed to break us down a wee bit, we gave away a few too many penalties but we managed to hold on in the end.
"It was only by the skin of our teeth, though. I don't think you can get much closer than that. It was just the bounce of a ball in the end."
Leinster trailed 12-6 at half time at the Stade Chaban Delamas but a Cian Healey try shortly after the break eventually separated the two teams.
And while critics suggested Clermont's powerful end to the first period would see the Top 14 team push on towards the Twickenham final, Boss knew his Leinster team-mates would really step up to the mark in the final 40 minutes.
"We've got a strong squad and we've got a lot of faith in each other," added Boss.
"We felt like we'd dominated for 20 minutes and then for the next 20 minutes we didn't really feature.
"We felt like the game was passing us by a little bit so we needed to take the game by its horns. A number of guys in different positions really stepped up.
"That try was crucial and it proved to be the difference in the end."