Add the whole flank steak or skirt steak to the slow cooker. If the steak is too large to fit into the slow cooker, cut into 2 or 3 smaller pieces.
Combine the soy sauce, water, orange marmalade, garlic salt and pepper and mix well with a whisk.
Pour the sauce over the flank or skirt steak and cook on high for 3-4 hours or on low for 5-7 hours, or until the meat is tender. Cook times will vary slightly depending on the slow cooker. Make sure the meat is tender before removing it.
15 minutes before the steak is finished cooking, add about 1 cup of the sauce to a bowl with the corn starch and mix well with a whisk. Pour the mixture back into the slow cooker.
Prepare the rice and frozen broccoli according to the directions on package.
Once the slow cooker has finished cooking, remove the steak and allow it sit for 10 minutes before slicing it against the grain.
Serve the steak over a serving of rice. Top with a few pieces of broccoli. Pour the sauce over the steak and broccoli