The Church of St Michael the Archangel, Analeentha, Cork, has provided an outdoor speaker to let as many people as possible take part in her funeral.
Miss Buckley, 24, was reported missing after a night out in Glasgow on April 12th.
Police found her body at a farm north of the city four days later.
Alexander Pacteau has been charged with her murder.
The service, which begins at 2pm, will feature readings by Karen's cousins Padraig Hurley and Jennifer Killeen.
Priest, Fr Joseph O'Keeffe, is expected to say that Karen's death "seems so utterly inappropriate" and that "it violates our sense of order".
A church notice about the service said: "Sadly missed by her heartbroken parents, brothers, grandmother, uncles, aunts, sister-in-law Niamh, cousins, relatives, neighbours and her many friends.
"May she rest in peace."