A "flat beater" is a kitchen tool, usually made of metal, with a flat or paddle-like shape. It is often used in a stand mixer to mix ingredients like dough or batter. Full definition
One tip I discovered a while back for easily shredding chicken — remove boneless chicken pieces from crock pot & put in bowl of stand mixer; using flat beater, turn on low for a minute or two to quickly shred chicken, then pop back into crockpot & mix back into sauce. (spendwithpennies.com)
Remove Spiralizer from stand mixer; attach flat beater to stand mixer. (blog.kitchenaid.com)