Mince spinach with a knife and stir-fry them in a non-stick pan with melted butter; allow the excess water to drain and let them cool down.
Sift the ricotta cheese in a bowl and add spinach and salt, then stir to mix ingredients well.
Take the focaccia square, cut it into two horizontally and grill it in the oven for a few minutes to the highest temperature.
Spread the base mixture with spinach and ricotta cheese on the lower part of the focaccia and complete with the slices of bologna. Close with the other half of the sandwich, slightly press it and serve immediately.
A useful tip? Divide the focaccia into four equal parts, so as to obtain 4 tiny delicacies!