Slot Machine Payouts Are Not Random - Here's Why

'What slot' is more general and is used when asking about any slot without specifying a particular one On the other hand, 'which slot' is used

Utility that highlights which items can be placed in an item slot

which slot does washing powder go in By Halvorson Media Group · Stake — Best Slot Machines in the Industry · Cloudbet — Best Slot Machine Games

which slot games pay real money slot A slot is a narrow opening in a machine or container, for example a hole that you put coins in to make a machine work He dropped a coin into the slot