Thaw spinach in the refrigerator according to its package. Squeeze thoroughly, then loosen the compressed leaves. Drain and chop the artichoke hearts. Thawing time is additional to the active preparation estimate.

Use a suitable small slow cooker, approximately 3 quarts, following its fill instructions. Combine spinach, artichokes, sour cream, mozzarella, Parmesan, garlic and pepper in the insert. Distribute small cream cheese cubes through the mixture. Do not add water.

Cover and cook on LOW for approximately 2–3 hours. Stir briefly after about an hour, then check periodically without leaving the lid off unnecessarily. Cooker performance varies; the 3-hour cook time shown is a planning allowance.

Stir thoroughly so the melted cheese blends evenly. Check several places with a food thermometer and heat the casserole-like dip to 165°F (74°C) before serving. If it is not evenly hot, continue cooking and checking. Taste before adding salt.

Serve with sturdy vegetable pieces and a spoon. Use WARM only after cooking and only if the food remains at or above 140°F (60°C), verified with a thermometer. Stir occasionally and avoid prolonged cooking that dries the edges.

Transfer leftovers to shallow covered containers and refrigerate promptly. Do not use the slow cooker to reheat refrigerated leftovers; reheat by microwave, stovetop or oven to 165°F (74°C) throughout.