In a 3 ½ or 4-quart slow cooker, combine the undrained tomatoes, squash, water, onion, and the seasoning packets from the couscous mixes.
Cover and cook on the low-heat setting for 4 to 6 hours or on the high-heat setting for 2 to 3 hours, until vegetables are tender.
Turn off the cooker.
Stir in the dry couscous from both packages, ensuring it is submerged in the liquid.
Cover and let stand for 5 minutes. The couscous will absorb the liquid and become fluffy.
Fluff the couscous mixture with a fork and serve topped with toasted almonds and, if desired, raisins and fresh cilantro.