So I would like to use FOK/IOC orders to avoid slippage. Is this possible? Let say I want to SELL 10,000,000 and the current price is at 60,010. I want to make sure my order gets filled without “slipping” below 60,000. If I place an FOK order with the limit price param at 60,000 does that work? Or does FOK only look at the best bid “level” (in this case 60,010) and if it can’t fill exactly at 60,010 then my orders gets cancelled. In that case its basically useless cause there will almost never be 10,000,000 at a single bid level.
The article above explains what are FOK/IOC orders. Basically, FOK order means that the order is either fully filled or killed. IOC order means that the order is filled immediately with the price (may be partially or fully depending on the market) and cancelled if not fully filled.
From your situation, i believe that what you need is to place an OCO (One cancels the other) order. The explanation can be found in the article. The order allows you to place 2 types of orders in an order, a stop-loss order and a limit order. Your stop loss would be placed at 60000 and limit order will be placed at 10,000,000.