Designing a database of Recipes Task

I need database design to record Recipes.


Recipes can contain several Ingredients and several ordered HowToSteps.
Each HowToStep can be split into ordered HowToSections.
A single recipe can contain a mix of several (ordered) HowToStep and (ordered) HowToSection elements.


My Solution


Table HowToSection with FK to the table HowToStep with FK to the table Recipe.
Table Ingredient with FK to the table Recipe.


Issue

I have no idea how to handle a business rule which stipulates that 


"A single recipe can contain a mix of several (ordered) HowToStep and (ordered) HowToSection elements".
You'd have a:

RecipeSteps table containing, recipe_id, stepnumber for order, and a HowToStep ref

And:

RecipeSections table containing, recipe_id, sectionnumber for order, and a HowToSection ref

The stepnumber and sectionnumber need to be non overlapping (per recipe_id for the pulling in the steps/sections in an order.