The Sheffield United midfielder tested positive for Covid-19 and was quarantined before the Scots flew from their training base in Spain to Portugal last week for the 2-2 friendly draw against the Netherlands in Portugal.
David Marshall, Stephen O’Donnell, Nathan Patterson, Grant Hanley, John McGinn and Che Adams had been left behind in Spain as a precaution but all returned and were involved to some extent in the final warm-up game, a 1-0 win over Luxembourg in the Stade Josy Barthel on Sunday.
Boss Clarke confirmed Fleck will come back into consideration when he returns to the squad but is probably not in the mix for the opening game against the Czechs at Hampden Park on 14 June, which comes before the trip to Wembley to play England and a final group game against Croatia in Glasgow.
Clarke said: “He is up for consideration for the tournament.
“John will join us in the middle of the week.
“He will get the option when he gets out of quarantine to go home for 24 hours to see his family or he can join us straight at the training camp.
“Because he is in his room isolating it would be a long shot that he is ready for the first game but he is certainly ready for the next two.”
Clarke was pleased with the warm-up double header which saw international debuts for Chelsea’s 19-year-old midfielder Billy Gilmour, Celtic playmaker David Turnbull and Rangers’ 19-year-old right-back Patterson and which meant Scotland have lost only two matches in 16 as they prepare for their first major tournament in 23 years.
He said: “It has been a good camp training-wise. We have worked well and we managed to get the nuts and bolts of how we want to play our system across to the players.
“And now leading into the tournament, it is about fine tuning toward certain opponents, which will require different personnel to cause them a problem.
“So lots to think about but that is the only way you want it as the head coach.
“Two defeats in 16 games, a freshness in the squad with the young boys who came in .
“They have done well, taken part in the group and training and have made contributions, they have their caps now.
“It puts a little bit of pressure on the senior ones, so things are looking good.”