Sandwiches

I prefer my sandwich cut in half. If the sandwich is made of sliced bread, does it matter when i cut it half: before or after making hamotzie?

If i make a sandwich from a shaleim, like a bun or a roll, should i make hamotzie on the shaleim, slice it, and then assemble the sandwich, and then take a bite? It might be a few minutes of assembly. What is the best order of operations?

In your first question , ideally the blessing should be said on the bread when it’s whole, and then cut in half.

Regarding your second question, it would not be worthwhile to wait while you make your sandwich. Therefore the best thing would be to make the blessing on it whole, cut an olive size piece and eat it, and then make your sandwich. If that is not practical, make your completed sandwich then make your blessing.