The Portion starts with the words: וַיַּקְהֵל מֹשֶׁה אֶת כָּל עֲדַת בְּנֵי יִשְׂרָאֵל, “Moshe assembled the entire assembly of the Children of Israel…”. (Ex. 35,1) He gathered all the people and his purpose was to instruct them in building the Mishkan. He first reminds them to observe the Shabbat as previously instructed. Rashi explains that he was telling them that although they are about to build the holy Mishkan, they were not to do any construction on Shabbat.
It is strange that in instructing the building of the Mishkan Moshe gathered all the people. He did not do so in all the other Mitzvot of Hashem. With other Mitzvot he first taught them to Aharon and them to Aharon’s children and so forth. There was a definite method. For the Mishkan he gathered all the people.
Perhaps the reason for this different approach is because of what happened with the destruction of the second בית המקדש. We are told that the Temple was destroyed because of שנאת חינם, unfounded hatred. Hence Moshe wanted to gather all the people in building the משקן so that the people will all be united and there would be no different factions.
This is a worthy objective that we should keep in mind in working with others to create an important project. There must be agreement at the start as to how things will be carried out.