Really difficult to pull off. You don’t need perfect luck for this, but you need above average luck for sure. The key is to flinch the Charizard and make sure it doesn’t get attacks off. Once you get through the Charizard the sides will have gone down by now, and it now depends on flinches. Getting through the Charizard is the hardest part though.
5/5 10/20 Garchomp with CS2, Sand Screen / Surging Sand / Ramming Speed build.