How to set timing of timing belt after rebuilding heads

Hey,

those images came across so small they blur out when I enlarge them. I do have timing diagrams I got from Hyundai. We did rebuild the heads, and set the DOHC cam chains on each side. And we are double checking the setting of the timing belt. We set piston #1 in the rear head to TDC (we believe this means it is TDC of its compression stroke?) And we set the three sprockets with marks on their marks. That is the two cam sprockets and the crank sprocket. We are pausing here to triple check as we are quite aware this is an interference engine. What are some double checks to do? (Like a position of a piston in the front head, etc). And have we done everything. With the three sprockets on their marks and piston #1 at TDC?
And does that mean piston #1 is TDC on compression stroke?

THank you very much !

Ok, that worked and we have done that alignment of the marks. Here is our more specific question :

When we put the chains on the cams we put it initially at the 3 and 9 in the colored links. We had the cams positioned to have no spring tension. In this position the sprockets are around 45 degrees off their mark.

Then when we put on the sprockets on they were not aiming at their respective marks, so we turned each cam sprocket independently clockwise to come to its mark.

Then next we turned the crank sprocket to its mark.

Then we checked and the #1 piston is up (so it is TDC or close to TDC).

Is this accurate? Or do we need to put the chains on the cams while the sprocket is on its mark and there is spring tension?