The Garuda won the semi-final 2-0 on aggregate after beating their opponents 1-0 in the first leg.
A first-half stunner by striker Christian Gonzales was enough to seal Indonesia's progress into the final with Malaysia, who shocked defending champions Vietnam in the other semi-final.
Despite being the dominant side during the match, Riedl admitted Philippines made it tough for his side.
"I think this sort of game is not good for weak nerves," the Austrian said.
"Our opponents made it very difficult for us to win the match today. They had a lot of set plays from throw-ins and corners and each time it was very dangerous for us.
"In the second half, we could see our players getting nervous. Philippines were getting the ball into box and they made things very dangerous for us.
"Unfortunately, we couldn't score a second goal which would have made things a little easier for us. We had chances but we missed those opportunities. However, at the end it was the result that I think that we deserved and we are through to the final.
"I must thank the players for their performance. When you play against touch opponents who are very much bigger and taller than you, it is difficult to do anything without fouling them. So you have to play very smart and they did that tonight."
The 61-year-old defended his players' fitness, insisting they were physically ready for the challenge against the Filipinos.
"The physical fitness of our players was very good but when you play against bigger players, it is difficult. We continued to create chances in the second half but when they started to come forward, it was hard to contain them because of their size advantage.
"For us, today's game was probably our most difficult game of the tournament because of how physically strong the Philippines are. For me they are like a European team, not a Southeast Asian team. Playing against big players like they have, it is harder to break it down to one-on-one battles.
"We were not looking for a good game today; we were looking to reach the final. In such a game, you don't look to play good football all the time. Of course we can play good football at some points during the game but you also have to be prepared to battle to deal with their long throw-ins and headers."
Indonesia thumped Malaysia 5-1 in their opening match of the tournament but Riedl has warned his side it would be no easy task to repeat the feat in the final.
"The final will be a typical clash between two neighbours. Of course we beat them 5-1 during the group stage but we felt that the score did not reflect how close the game was. We are expecting that the score will be a lost closer game this time around.
"In the final, we have to try not to be as nervous as we were . In the last 25 minutes, our players began to let their nerves affect them and they began to slow down a bit too much."
The first leg of the final will be held in Kuala Lumpur on December 26 and the return match in Jakarta three days later.