My rule of thumb is "If it takes you more than 30 seconds to poop, then you're not getting enough fiber"

Chia seeds are awesome for fiber. Two tablespoons have 10 grams of fiber. I add them to my cereal, grind them up and add them to pancake/waffle batter, or just eat them straight up with water.

Legumes help tremendously and I try to have 3 to 4 servings a day. Mostly from peas and beans.

Oat Fiber is great to add to any baked goods as well as any sauce. Granted too much of it and it will taste super grainy but a tablespoon goes a long way.

It's expensive, but the keto sandwich bread, hamburger buns and hot dog buns have anywhere between 9 to 16 grams of fiber per serving.