we use sand, then foam, then tubes.
get 300 foot rolls, as that is the maximum loop length you are allowed.
most of the time, the tubes are 12" on center, 6" oc on the perimeter. with a sheet of graph paper,

I just did my own 2200 SqFt house, and followed this plan. In addition
I did the garage and covered porch. In all there's 6 zones, and
something like 10 coils.

One think I would suggest is when you have the pipes that come up
though the concrete, feed the pex through 1" electric conduit 90 degree
elbows. This keeps the pipe from kinking or angling up during the
pour. I purchased some of the metal channels used in commercial
electrical applications to support the manifolds during the pour (mine
are out in the concrete field. Drive it into the dirt plum before
pouring and set channel in the concrete. With a little rigging, I was
able to put about 30# of air in the pipes and that way knew if they
were damaged during the pour.

Wirsbo has compression splices that were on hand "just in case" the
pipe was nicked during the pour...thank goodness we didn't need it.

I was told that the bubble sheet wasn't effective as the foam. DAGS and
you'll find pros and cons...I choose to use Owens Corning Foamular250.
They have 2 grades of pink 2" foam, one rated for under slab one is
not. In addition, I put 6 mil plastic under the foam, to keep ground
moisture from migrating up into basement floor. Maybe overkill...but
for a few bucks...I wanted a dry basement, and this is just one more
element.

Best of luck...

DAC