This is the best internet article on the biblical basis for being slain by the Spirit:
https://www.bible-knowledge.com/slain-in-the-spirit/
But surprisingly, neither this article nor any others on the internet identify the most relevant prooftext:
"If all prophesy, an unbeliever or outsider who comes in is reproved by all and called to account by all. The secrets of his heart are revealed, and so, FALLING ON HIS FACE, he will worship God (1 Corinthians 14:24-25)."
In the context, Paul presents his expectations for the proper exercise of the gifts of speaking in tongues and prophecy during public worship. Note his expectation for how the work of the Holy Spirit impacts the beneficiary of a prophetic word: the beneficiary neither sits there to absorb the Word nor kneels down in prayer; rather, he
falls on his face, overwhelmed by conviction from the Holy Spirit.
This is the pattern expected by Paul, but not a prescription for how it always must be. In the OT people often fall on their face when they experience "the glory of God." But the experience of being overwhelmed by the Spirit does not mean coerced falling. In a highly emotional or ecstatic state falling can seem natural or inevitable. Thus, a highly emotional Jesus does not lie down or kneel down in Gethsemane to pray; rather, He "fell on the ground (Mark 14:35)."