Fullback Jackie Shiels, taking over the number 15 jersey and the kicking tee from Munster's Niamh Briggs, added 10 points from the boot in a flawless display.
With ten changes made following Ireland's famous victory over New Zealand, Head Coach Philip Doyle has given his entire squad a taste of World Cup rugby.
A handling error from Kasakhstan's Algerym Daurembayeva five metres from her own line gave Ireland the platform to attack early on.
An awarded penalty which Ireland kicked into touch followed a smooth line-out in the opening 40 minutes and it laid the foundation for flanker Lynch to break a central tackle and ground the sixth minute score under the posts.
With the Kazakh pack on top and Ireland unable to clear their lines, they forced their way over the try-line after 20 minutes, only to be held up in goal with impressive Irish defensive play.
Within minutes, though, they had their reward when lock Svetlana Karatygina spun free of another dominant maul to ground Kazakhstan's third try of the tournament which they failed to convert.
On the 36 minute, half back Tania Rosser scored a fine individual try finding a gap outside the 22 to score giving Ireland a 14-5 lead at the break.
Following the introduction of a new Ireland front row in the second half, dividends were paid as they forced a penalty try and the sin-binning of Marianna Balashova.
This created the space that allowed Tralee women Fleming raid the right-wing channel and sprint a full 60 metres to claim an impressive solo try sealing the bonus point.
Lynch claimed her second score 10 minutes from time and winger McGinn rounded off another flowing second half move after the clock had moved beyond 80.
Ireland's semi-final opponents will be confirmed later today as the line-up will be determined by seeding. The bonus point win leaves Ireland on 13 points with England, Canada (who play eachother) and France on 10 points before kick-off.
Ireland: Jackie Shiels (Richmond/Exile); Vikki McGinn (Blackrock/Leinster), Lynne Cantwell (Richmond/Exile) (capt), Grace Davitt (Cooke/Ulster), Hannah Casey (Saracens/Exile); Tania Rosser (Blackrock/Leinster), Larissa Muldoon (Bristol/Exile); Fiona Hayes (UL Bohemians/Munster), Gillian Bourke (UL Bohemians/Munster), Kerrie-Ann Craddock (Saracens/Exile), Laura Guest (Highfield/Munster), Orla Fitzsimons (St. Mary's College/Leinster), Sharon Lynch (Old Belvedere/Leinster), Siobhan Fleming (Tralee/Munster), Paula Fitzpatrick (St. Mary's College/Leinster). Replacements: Fiona Coghlan (UL Bohemians/Leinster), Ailis Egan (Old Belvedere/Leinster), Sophie Spence (Old Belvedere/Leinster), Claire Molloy (Bristol/Connacht), Nora Stapleton (Old Belvedere/Leinster), Alison Miller (Portlaoise/Connacht), Ashleigh Baxter (Belfast Harlequins/Ulster).
Kazakhstan: Algerym Daurembayeva, Oxana Shadrina, Anne Yekovleva (capt.), Balzhan Kolshybayeva, Luudmila Sapronova; Svetlana Klyuchnikova, Amina Baratova: Yelena Muradova, Yelena Yevdokimova, Olga Baktiquzina; Lyudmila Matiyeva, Svetlana Karatygina; Symbat Zhamankulova, Kundyzay Baktybayeva, Marianna Balashova. Replacements: Irina Radzevil, Yelena Rogacheva, Yelena Kiryushina, Karina Proskurina, Anastassiya Khamova, Aigul Dairbayeva, Olga Sazonova.