Hi,
You can pick one switch in a stand alone mode and configure it as stack master (with higher priority 0-15) and than attach other switches to it as stack members. Just remember every time you want o add a new switch to the stack, make sure the new switch is turned off before connecting the stacking cable. As far as the config, if you attach a switch to a stack as a stack member, the master with override the config. Also, make sure all switches you are stacking together have the same exact IOS and license level.
Have a look at this link for more info:
A standalone switch is a switch stack with one stack member that also operates as the active switch. You can connect one standalone switch to another to create a switch stack containing two stack members, with one of them as the active switch. You can connect standalone switches to an existing switch stack to increase the stack membership.
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/ha_stack_manager/configuration_guide/b_hastck_3se_3850_cg/b_hastck_3se_3850_cg_chapter_010.html
HTH
