I agree with Becky - dust it really well and don't try to clean out all the flour afterwards - if you use linen you won't get the marks. I have the smaller one since I tend to make smaller loaves ( 1 or 1 1/2 pounds) and it works very well. Here's a photo of a sprouted wheat loaf that I made - it shows both the circular lines and the nice contrast the flour makes with the flashes:
