You could try replacing some of the water with vodka, old trick for crispy pie crust

Too much water, make sure they are very thin, lower heat and cook longer

After you finished baking, turn the oven off and let them cool in the oven overnight.

Try ammonium bicarbonate instead of baking soda


https://bakerpedia.com/ingredients/ammonium-bicarbonate/

I have been trying a recipe for homemade crackers sort of like Italian rosemary crackers. I want them to be very hard and crunchy with a real snap but they keep coming out tender. They use flour, water, baking powder, olive oil, salt and rosemary.

Any ideas with the technique to use?