Note about cooking time: Your crockpot may differ in temperature than mine, I suggest cooking this for 4 hours on your first go-round of this dish. 6 hours in the crockpot seems to be giving a lot of people "shredded" beef instead of slices, so decrease cooking time by 2 hours and go from there. Mine turned out fine with 6 hours.
If you are using frozen broccoli florets, you do NOT need to defrost them prior to putting them in the crockpot. You add them in at the same time as you add the cornstarch slurry. As stated in the instructions, after you add the cornstarch slurry, you cook for 30 more minutes. This should be more than enough time to cook and defrost your broccoli florets.
If you're using fresh broccoli, you do NOT need to steam them prior to putting them in the crockpot. You add them in at the same time as you add the cornstarch slurry. Since you cook an additional 30 minutes, this will ensure that your fresh broccoli will be cooked through.
Yes, you put the meat in the slow cooker raw, in sliced pieces.
Source: adapted from BS Recipes