Slice kernels from corn cobs. (Note: If you’d like, you can save 2 or 3 of the cobs and add them to the chowder as it cooks - this will help to enrich the stock with even more corn flavor.)
Heat a large skillet over medium heat and add bacon. Saute bacon until crisp, ~10 minutes. Transfer bacon to a paper towel-lined plate and drain off all but about 1 Tbsp grease from the skillet.
Return skillet with bacon grease to medium heat and add butter.
When butter melts, add onion, salt, and sugar and saute until onion is soft, ~4 minutes.
Add garlic and cook for 2 minutes more.
Transfer the onions and garlic to the bowl of a slow cooker.
Optional: If you’d like to garnish the finished chowder with some corn kernels and / or crispy bacon, set about 1 cup of corn kernels and 1/4 of the crispy bacon aside before filling the slow cooker.
To the bowl of the slow cooker, add corn kernels, bacon, thyme sprigs, bay leaves, potatoes, stock, and water.
If you reserved any corn cobs, nestle those into the chowder.
Cover and slow cook until potatoes are tender, high for 3 to 4 hours or low for 7 to 8 hours.
When you’re ready to serve the chowder, remove and discard thyme sprigs, bay leaf, and corn cobs.
Stir half-and-half into chowder.
Optional: You can serve the chowder as-is, or blend some of it to create a creamier / thicker base. Use a stick / immersion blender (or transfer a few cups of the chowder to the blender) and blend until smooth.
Taste the chowder and add some salt and / or black pepper, if needed.
Serve chowder garnished with reserved corn kernels, bacon, green onions, and / or cheese.