In my insane days of buying giant blocks of Options I would use a Reserve Book showing 200 Contracts and wait until they would get hit, when a stock is moving fast upward, you can get out of those contracts 2000 contracts but it's best to work your order out manually on a high flying stock.
I watched a Trader unload 3 blocks of 15,000 contracts by using 500 share Reserve Book, these were not prearranged because I bought 2000 contracts from this seller. I was confused why this Options seller was dumping these contracts hard even though the price of the stock had great volume and was going to blow past $16.00+ in my mind (At $15 he started to sell all those contracts) and it took the physical stock to hit $17.5 before all his contracts were dumped. Why did he unload so many contracts at $2.00 $2.50 and $2.75
This nutty stock did hit $21.00 and I sold my contracts at 200 a pop at various prices on the upward madness. I thought there must be a reason why somebody would dump that amount of contracts so I emptied out everything because I was nervous he knew why he was selling. I was wrong, stock kept going up the next day to $25 and past $30, one of those real examples of why did that seller dump all those contracts and should I have allowed his dumping to taint my thinking? That was a few years ago but I still see when big dumping takes place, often the stock craters so the 3 out of 10 that continue moving upward don't steer my mind away from following the Giants and their moves. I hope this is what you were thinking about when you were asking how the Big Giants like the 45,000 contract seller worked his position out.