The 20-year-old was called upon at the last minute when Glen Johnson was ruled out due to a jaw infection.
Saturday's clash at the Emirates was Flanagan's first Premier League start in 19 months and his first appearance since the FA Cup win at Mansfield Town in January.
Manager Brendan Rodgers selected the England Under-21 international ahead of Martin Kelly and the right-back admits there were nerves - but he enjoyed his Premier League return, despite enduring defeat.
"It was great to be back in the team and get the chance to play but it would have been more enjoyable if we had got a decent result," he told the Liverpool Echo.
"I only found out I was playing a couple of hours before kick-off. We had a team meeting beforehand and it became clear that Jonno [Glen Johnson] was struggling.
"The manager told me I was starting and I just had to make sure I was ready. It had been a long time since I last played in the Premier League.
"There were a few nerves but once the game started I was just focused on getting into the game and doing my job for the team.
"I felt like I did okay but to be honest it was all about the result and we were all frustrated by the defeat."
Flanagan has endured plenty of frustration since making his debut against Manchester City in April 2011, spending the majority of last season on the sidelines injured.
But he insists he is ready to fight for a regular place in Rodgers' plans.
"I had a tough time with injuries but hopefully that's all behind me now," he added.
"I've just been training hard, giving 100% and trying to force my way into the manager's plans. Hopefully I can get another chance and keep showing what I can do."