Hensol - Gareth Bale headlined the 23-man Wales squad for Euro 2016 announced by manager Chris Coleman on Tuesday, while Joe Ledley was included just three weeks after fracturing his leg.
Bale, Wales's top scorer in qualifying with seven goals, arrives fresh from scoring in the penalty shootout as Real Madrid defeated Atletico Madrid on Saturday to give him his second Champions League title.
Ledley, capped 62 times, fractured his left fibula during Crystal Palace's 2-1 win over Stoke City in the Premier League on May 7, but took part in Wales's training camp in Portugal last week.
"Joe looks very good," Coleman told a press conference at the Welsh base in Hensol.
"He trained on the grass in Portugal, albeit with the medical team, but he played a huge part in the campaign and is a big part of this team.
"The work he has put in is incredible and he looks good. With the injury he has had he is ahead of his work in his rehab.
"We will assess him and we will know more in the next week. But at the moment I think he has a good chance of playing against Slovakia."
Newcastle United left-back Paul Dummett and young Wigan Athletic midfielder Emyr Huws were among the players who dropped out of Wales's provisional 29-man squad.
Wales, who have qualified for their first major tournament since the 1958 World Cup, play their final warm-up game against Sweden in Stockholm on Sunday.
Coleman's men open their Euro 2016 Group B campaign against Slovakia in Bordeaux on June 11 before playing neighbours England in Lens five days later and then tackling Russia in Toulouse on June 20.
Wales 23-man squad for Euro 2016
Goalkeepers: Wayne Hennessey (Crystal Palace/ENG), Daniel Ward (Liverpool/ENG), Owain Fon Williams (Inverness Caledonian Thistle/SCO)
Defenders: Ashley Williams (Swansea City, capt), James Chester (West Bromwich Albion/ENG), Ben Davies (Tottenham Hotspur/ENG), James Collins (West Ham United/ENG), Chris Gunter (Reading/ENG), Neil Taylor (Swansea City), Jazz Richards (Fulham/ENG)
Midfielders: Joe Ledley (Crystal Palace/ENG), Joe Allen (Liverpool/ENG), David Vaughan (Nottingham Forest/ENG), Jonathan Williams (Crystal Palace/ENG), David Edwards (Wolverhampton Wanderers/ENG), George Williams (Fulham/ENG), Aaron Ramsey (Arsenal/ENG), Andy King (Leicester City/ENG)
Forwards: Gareth Bale (Real Madrid/ESP), David Cotterill (Birmingham City/ENG), Hal Robson-Kanu (Reading/ENG), Simon Church (Aberdeen/SCO, on loan from Milton Keynes Dons/ENG), Sam Vokes (Burnley/ENG)