In reality, with a little work they’re not that illiquid, since regardless of how wide the listed spreads are, MM computers are programmed to fill wherever the market is, and they’re generally willing to buy for a couple cents less than they’re willing to sell. Knowing this, make an educated guess (based on recent sales of that contract or infer from ones nearby in price) and then just move up and down 5c at a time (or better yet, 1c at a time on Schwab) until you get a fill. Then you can start buying or offloading around that price. Sometimes the first fill can be improved upon on subsequent buys/sells so I’ll generally just do 1 contract when I’m scouting the market, and then try to get a better fill with my volume.