This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
How can you sit seiza for that long?
I thought Koichi would make me do seiza, but he was as generous as a Buddhist priest and excused me for being late.
I knelt in seiza for so long during the Buddhist memorial service that my legs were completely numb.