(Note: parsnips cook faster than carrots, so I put the carrots next to the ceramic pot and put the parsnips in the middle. Small red potatoes dotted the outside.)

Cook on low for 6-8 hours, till tender.
Remove batch from the slow cooker VERY CAREFULLY, put in a bowl and chill till next day.
When it's time to eat, remove the meat from the bones. Put the meat and veg into a large pot and heat. To the juice which remains in the cooking bag, add the peel of one lemon, grated, and the juice thereof.
Stir in the rosemary/marjorum. Add juice to the pot and heat through.

Add salt and black pepper at the table.   
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I like my microplane for grating the lemon peel.

https://www.amazon.com/Microplane-40020-Classic-Zester-Grater/dp/B00004S