Where does “саставити” come from?

саставити (Serbo-Croatian) comes from Serbo-Croatian ставити, from Proto-Slavic stàviti.

Ancestry of “саставити”, step by step

Step	Language	Word	Meaning
1	Serbo-Croatian	ставити	to put, place; to put on, wear
2	Proto-Slavic	stàviti	—

саставити — Etymology, Origin & Word History | Etymology Explorer