Clean the chicken breasts of any fat and cut them into approx. 1" cubes. Toss the cubes with lemon juice and salt and set aside for a few minutes, while you prep your baking sheet.
Line a baking sheet with aluminium foil. The baking sheet has to be big enough for you to be able to spread all the chicken cubes in on layer. I use a 16X11 pan but it can be smaller than that, too. Make sure your baking sheet has a lip to catch the juices from the chicken as it cooks. You may also use a large glass baking dish instead.
Spread the cubed chicken on the pan/dish in a single layer.
Sprinkle with the garlic powder, crushed black pepper and any other spices that you may be using.
Bake for 20-30 minutes or until the chicken reaches an internal temperature of 165°F. Do not overcook or it will dry out the chicken breasts.
Let the chicken cool on the counter until it's easy to handle.
Use a weighing scale and divide the chicken cubes (NOT the juices) equally into 16 airtight containers. I usually cook for two so I divide mine into 8 containers. Refrigerate for up to 5 days or freeze them for longer. You may also save the juice and use it as a substitute for chicken broth in recipes.