Start the diagram by listing your known quantities v0, vf and `dt along the top of your diagram (the 'first level').
(vAve = (v0 + vf) / 2, since acceleration is uniform. This would be indicated by lines connecting v0 and vf to vAve, the latter being on the 'second level'--below the top of the diagram.
`ds = vAve * dt.
vAve = `ds/`dt Good, bu you didn't indicate how vAve is obtained. You would put `ds on below the rest of the diagram, and connect vAve and `dt to `ds by two lines.
aAve = `ds/`dt aAve would go below the rest, and be connected to `ds and `dt by two lines.
See also the diagrams in the Introductory Problem Sets.