I wear a size 6 1/2. Your suggestion was to ask for the next size up as the slippers do not come in half sizes. And so, I ordered a size 7. One would expect slippers of this type to feel cozy on one's feet. Not so. The ones that I ordered are too large to be comfortable. I am disappointed. A size 6 would have been more on the mark. I think you should change your instructions to read "order the next size down if you are a half size."
The Wicked Good line of Slippers is so good that my boot-style pair just wore out after over 15 years of regular use. However, unlike my old boot style, the moccasin I ordered does not have much of an arch support. If this doesn't matter to you, they are an excellent slipper. If it does matter, they're merely "good."