100g carbs is pretty low already, but you can do either one of two things.
Cycle carbs like CKD, by running 20g for a week or so and having a re-feed or carb load one day of the week with any kind of carbs you like. I ran a vesion of this where I was 50g or less during the week and I just had a cheat day, pizza/ice cream whatever, but I would avoid binging (I was bad with that). Pick one, not two or more - if you are going from 2k calories to like 4000 in my example.
Next is, dont carb up at all. Stay 40-75g carbs all the time. Seriously bro the strict dieters I know of eat more than 2k calories and are doing 75g daily (male not female), so really for only 2k calories you aren't very low at all if you are looking at doing keto.
I would have oatmeal for breakfast and no other carbs during the day other than post-workout (which doesn't count if you do 25 or less and use fast acting).
There are a billion ways to diet though.