Add seasonings and stir. Add water (or stock or broth) and increase heat to high.
Rinse red lentils in a colander and add to soup. Cover and bring to boil.
When mixture comes to a boil, stir in tomatoes, molasses, and juice. Return to boil and then reduce heat.
Simmer for 50 minutes, stirring occasionally.
Stir in chickpeas and continue cooking for 10 minutes.
Add salt to taste. The amount of salt needed will depend on the amount already in the tomatoes and chickpeas.
Notes
I've made this in my slow cooker in the past, but it's been a while so I don't remember the exact cooking time for it (although the words "exact" and "slow cooker" probably don't belong in the same sentence.) However, slow cookers are very forgiving when it comes to soup cooking times. I would probably cook the lentils and tomatoes for about 4 or 5 hours and then an additional hour once the garbanzos have been added. All slow cookers are different, so experiment with yours to find the best cooking times.