This is the 247th most frequent Swedish word.
slog
"Hit" or "struck" (past tense of "slå").
Here, 'slog sig ner' means 'sat down' or 'settled down', using a reflexive form of 'slå' to indicate the act of settling or sitting.
Vi slog oss ner vid elden och började prata.
We sat down by the fire and started talking.
The word 'slog' here is used as the past tense of the verb 'slå', which means 'to hit' or 'to strike'. It denotes a physical action of hitting the drum.
Han slog på trumman med glädje.
He beat the drum with joy.
In this sentence, 'slog' is used metaphorically to mean 'broke' as in exceeding or surpassing a previous limit or record.