The Brisbane winger, who has scored 10 tries in his past six NRL games, won a hotly-contested race for a spot in the Maroons' backline ahead of teammate Corey Oates and North Queensland pair Hamiso Tabuai-Fidow and Murray Taulagi.
There are spots on the reserves list for Tabuai-Fidow and Taulagi, while Slater said he would have been comfortable handing Oates a jersey too despite him missing the 22-player squad altogether.
As well as 19-year-old Cobbo, Cowboy Reuben Cotter was "one of the first written down" to debut at lock, while Pat Carrigan and Jeremiah Nanai, also 19, are both set to debut for their state from the interchange bench.
Slater allowed Cowboys coach Todd Payten to break the news in front of his NRL squad that six players had made the Maroons' 22, with Valentine Holmes at centre and playmaker Tom Dearden effectively 18th man.
But the former Origin fullback enjoyed the call to Cobbo.
"He said thank you a few times," Slater grinned.
"He's a likeable lad and he's taken the game by storm.
"He's really lit the game up - brings so much excitement - but he's doing alot right that we don't focus on as well.
"Which is a big reason why he's there."
Gold Coast captain Tino Fa'asuamaleaui will start in the front row but Slater has overlooked Titans' teammates Moeaki Fotuaika and David Fifita.
Cotter's selection means there's also no place for South Sydney's Jai Arrow, who Slater says has been relegated to the reserves due to depth in the position and not his hotel protocol breach that led to a suspension in last year's series.
St George Illawarra captain Ben Hunt has also been named at hooker, with Melbourne's Harry Grant in the utility role.
Slater said he's confident Grant will be fit to play despite him remaining in Melbourne as he overcomes a groin niggle and bout of the flu, but that Hunt's performances for the Maroons in recent years meant he had earned a starting role in any case.
The Maroons will assemble in Brisbane on Monday before travelling to the Gold Coast for their training camp ahead of game one at Accor Stadium in Sydney on June 8.
Queensland: Kalyn Ponga, Selwyn Cobbo, Valentine Holmes, Dane Gagai, Xavier Coates, Cameron Munster, Daly Cherry-Evans (capt), Tino Fa'asuamaleaui, Ben Hunt, Josh Papalii, Kurt Capewell, Felise Kaufusi, Reuben Cotter. Interchange: Harry Grant, Lindsay Collins, Patrick Carrigan, Jeremiah Nanai. Reserves: Tom Dearden, Jai Arrow, Thomas Flegler, Hamiso Tabuai-Fidow, Murray Taulagi.
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