I have touched on this at other times, as here, here, and here. In the present post I am simply emphasizing the point more directly potentially for future reference.
If you receive an IKEA table in the mail, you have the parts that go to make up a table, but they are not yet put together in the form of a table. But very obviously, the form is not an additional part that you need to make the table. One does not say, “We need six parts for the table: the four legs, the tabletop, and the form of the table.” The form is something additional, but it is not an additional part. It is the “being put together as a table” that the parts require in order to be a table.
To say that the parts exist “in the form of a table” is also an informative expression here. One speaks as though “the form of a table” were a place, somewhat like Newton’s absolute space, in which the parts of the table exist together. This idea is helpful because just as Newton’s absolute space does not actually exist, so there will be analogous errors about form, as for example the idea that form is an additional part. Likewise, understanding the actual truth about place will help us to understand the truth about form.