You can snack within your eating window if you prefer.
When I’ve had my fill, I stop eating.
If I’m short on calories for the day, I eat a salad with an olive oil-based dressing and it’s calorie-heavy.
In my opinion, it would be easiest to take your caloric intake, divide it by your eating window, and spread your calories evenly throughout. It’s a bit of a hassle I’m sure, but you would certainly avoid large meals.
I don’t know who said snacking is discouraged but I usually fast 18-20 hours and almost always break my fast with a small easy to digest snack like a handful of almonds or a small yogurt. If I break my fast with a normal or large meal I frequently will get stomach cramps immediately after my meal.