I usually don't do anything when there's a flash crash, and sometimes I only find out about it afterwards
They're normal in the market
But a flash crash can liquidated my positions in DeFi loans
So I need to stay alert, or leave a good health position
Sometimes a flash crash can be good if you leave an order, for example, you can leave a order to buy BTC at 90k, maybe a flash crash can trigger this order for you