I have a small square(ish) tupperware-type dish (5 inch by 5 inch) that I use to make the "muffin", making it about the size of a slice of bread and 3/4 inch thick. When it is cool I slice it horizontally to make two slices of bread for a sandwich. Perfect!
Sometimes I add a couple drops of almond extract or a small pinch of onion powder (not onion salt) to add a different flavour and mask the strong egg taste.
Today I bought liquid egg whites so I'm going to try them, cuz I think the result will be a less eggy flavour.
And - I don't like to use artificial sweetener and the OMM was the only thing I was using it for. I had debated trying the recipe without but didn't want to spoil a muffin. However, this morning I just realized that yesterday I completely forgot to put the sweetener in, and never noticed. It tasted fine and was the same bread-type result. So now I will just eliminate the sweetener totally.
Also, when I get it all mixed in the little dish I let it set for about a minute before I put it in the microwave. This lets the flax absorb some of the moisture and swell a bit.