The melocha of boneh is typically understood as building a house, part of a house, or a utensil. The gemorah in Shabbos 95a introduces a new application of boneh. To build food is also forbidden. The example given in the gemorah is the process of making cheese. After curds are seperated from the milk with a natural or artificial enzyme, these curds are then pressed together into a solid mass called cheese. The act of combining these pieces to create a new object is boneh. Some poskim say that boneh is only violated when making the cheese into a nice shape. See Magen Avraham O”H 340:17 and Nishmas Adam 93:1.
Some practical applications of boneh in foods would be making a watermelon basket, or pressing loose pieces of tuna fish, or egg salad together onto a nice shape. Some forbid making a nice arrangement of fruit. See Chayei Adam 39:1.

Rabbi Tzvi Aryeh Hyman, Mir Yeshiva
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