Place meat into a big pot (I like to use the pot I use for tamales), pour in 6 1/4 quarts of water, bay leaves, 6 garlic cloves and half an onion. Cover and bring to the boil over high heat. Then, lower the temperature to medium high and let it cook at a medium boil for 1 - to 1 1/2 hours or until meat is cooked and tender.
While meat is cooking, prepare the sauce, clean the hominy, and prep garnishes: Pour 3 cups water into a separate pot to boil. Remove stems and seeds from guajillo peppers and chiles de árbol (if using them). Don't be afraid to cut them in half or in pieces if it is easier. Put them in a deep bowl and add the rest of the garlic cloves and onion. Pour the 3 cups of boiling water over them, cover and let it rest for at least 30 minutes. You can leave them in the water until you are ready to make the salsa.
Wash the hominy kernels really well and leave them in a colander to drain.
Wash and slice the lettuce and radishes. Chop onions.
About 5-10 minutes before meat is ready, pour the hydrated chiles, garlic, and onion with the water into a blender. Add oregano and salt and mix until smooth. Set aside.
When meat is cooked, remove it from the broth with a slotted spoon, but leave the bones in the pot. Remove the bay leaves and any pieces of onion and garlic you happen to find, but don't stress too much if you cannot get them all out.
Add hominy and sauce from blender, stir with large spoon. Cover and cook over high heat until boiling again. Then, lower temperature to medium high and let it cook for another 20 minutes. Let rest for 5 minutes.
While hominy is cooking in the broth, shred the pork, and chop a piece of the pork skin in small pieces, then add the meat back to the pot.
Top each bowl of pozole with mounds of lettuce, chopped onion, radishes and a generous squeeze of lime or lemon.
Serve with tostadas.