You definitely don't need a mixing plate for dry salts, BUT it is handy. Set a 2 liter mason jar on it, put the lid on, when mixed flip the jar and the magnet sticks to the lid, then remove the lid and use your sauce. I like to use one to mix the epsom salt I add to my 30 gallon mix. I put a liter or so of water in it, weigh out 45 grams of epsom and dump it in, let it go while I measure the liquid feed components... Use it to make concentrate and then just measure that off if you please. I just like doing something else while the salts break down instead of shaking a jug or stirring a bucket.