$AMKR
Nice flag with size put writing today (bullish positioning)
"Alex, how do you know if these options are being bought or sold?"
Look at Implied Volatility (IV) on the far right. If options are being bought, this is typically increasing. If they are being sold (as in this case) the IV will decrease. Not always perfect but is a very good tell. Notice how the first line starts at 94 and continues to decrease.
This is a good tell in real time to make decisions on which direction the trader is betting on.
Real icing on the cake is to check open interest (OI) in the morning to determine if this entire position was held overnight. Remember open interest shows how many open contract there, NOT if they were bought or sold initially.