Divide the spices into the jars (each jar should receive 1 dill head, 1 Tbsp yellow mustard seeds, 2 cloves garlic, and about 2 tsp of red pepper flakes) and pack beans into the jars.
Meanwhile in a saucepan combine the water, pickling salt, and white vinegar and bring to a boil. Remove from heat and add to jars, adding a 1/2 inch of headspace. Tap the jars to remove air bubbles and seal tight.
Let sit until jars reach room temperature then refrigerate for at least 48 hours before consuming.
Notes
These beans can be stored for up to 2 months in the fridge.