I make this in the oven (obviously). Unless you make this super thin (which I do not like to do), this sandwich is not very conducive to being grilled and flipped. A sandwich press would be the best and most efficient way to make this, but I haven’t owned one in quite some time, so the oven method works for me.
Worth noting is that the original recipe was for an open-faced sandwich – which is how I prepared it for a long time. Personally, this is a lunch food for me and I just find it easier to take to work in normal sandwich form. However, if you go open-faced, stick with 4 slices of bread, but divide the tuna and cheese across all 4 evenly.