I always pour garage floors after the house is framed, this is usually industry standard practice. The garages are back-filled with the foundation so you want for the dirt to settle before you pour a slab.

Here is a picture from a house I did a while back, right after roof was installed the garage slab was poured.

Thank you so much! Would you recommend doing the same thing for basement floors/slabs?

Different climate. But I have always done the concrete after the framing is done as that has been the preference of the second and third generation concrete and drain contractors I've employed. When access is difficult, you just remove a section of subfloor and/or wall to get the chutes in.

If you pour before there's the protection of a structure, you risk digging and setting drains and concrete in a soupy mess.

Building on a slab is virtually unheard of in southern Ontario.

Our garge and porch slabs were not poured until later on. We did have our basement poured but we are finishing the entire basement.

As Worthy suggests, for any slab, If it rains soon after the pour, you would be in a difficult situation. For a basement slab, if it rains before the roof is on, you might need to pump the water out. I've never seen a slab poured before the roof was on but in a very dry climate, it might be a risk contractors are willing to take.

I've seen here and there some builders pour the slab before the framing stages and by the time the framing is completed and roof is installed, concrete slabs have all kinds of stains on them, from weather or natural elements like water, leafs, construction elements like sub-floor glue being dropped on it, rusted nails etc, not to mention some start framing before concrete is cured completely and lumber being dropped on it, etc.

It's not a good practice to do it before.