'how would I do it?'
you just 'do it'. the same as any other design. except you might find you need to put more things into one file, or start and end the table in different files, etc.
for instance:
header.php starts mega table, first row is header, spanning however many columns you'd have (lets say two). then opens a new row.
index.php is wrapped in a td as one big cell (but could also then embed a table inside the cell, with each post as a row, etc.), and closes it before including the sidebar.
sidebar.php is wrapped in a cell as well, the second column of the row.
footer.php closes the 'content and sidebar' row, makes another row for the footer, and then closes up the table.
-d