"Se poser" is when the subject is doing an action. And "se" is in accord with the subject of the sentence. So the bread can't do an action :) "Être posé(e)(s) " is the passiv form of the verb. So the subject is not doing the action but someone else, who is not always mentioned in the sentence. And because it's the verb "être " you always accord the particip (here "posé") with the subject (here "le pain" is masculine so just "é" at the end). Here this is that case. When we're speaking about bread, "boîte " is a bit strange. We prefer to use "corbeille", what you put on the table. So here the correct sentence in present form is : "Le pain est posé dans la corbeille" But in fact we would say "le pain est dans la corbeille" and "le pain est posé sur la table" but not really what you want to say... [emoji] If you want to use the futur (what you wrote), you just conjugate the verb "être " so "le pain sera dans la corbeille ", "le pain sera posé sur la table". I hope to have been clear !!