These amounts are per day
On day 1, place the ingredients in your jar, mix well and replace the lid.
Once the mixture starts to produce bubbles, this can be after just 12 hours, but could be as long as 3 days, scoop out (discard) half of the mixture and add a new half cup of flour and quarter cup of water.
Mix well with a fork, replace the lid.
Continue removing half the mixture and replacing it each day until your mixture is bubbly and very active. Now it is ready to use.
Each time you remove, say, half a cup of starter for a recipe, replace it with half a cup of flour and a quarter cup of water (the equal amount of flour, as amount used in recipe plus half that amount of water). You will not need to feed additionally on that day.
Please note that where the recipe asks for milk, butter or yogurt, this refers to any plant-based version that you prefer.