bonemeal custom grass to plant tall grass and flowers

Hi I'm brand new to using mcreator I've made a custom grass block and I'd like to be able to bonemeal it and have it spread grass and flowers (the flowers based on probability if possible so rarer ones don't spread too frequently) I've tried checking the procedure templates but I haven't seen one for what I want and am not sure how to work from scratch/didn't find any readily available tutorials for this. Any advice?