How do you solder this 24pin SMD IC+

I have limited experience with SMD and this is this is the first time I've encountered this. I ordered replacements and then removed the old ones.
There is a large pad on the bottom that is soldered to a large ground land on the board.

How do I solder this large ground under the IC?



The back side of the board has a land on the ground mirroring the front side (second image) with the same pinholes in it. Am I supposed to apply heat here to the backside until I see solder flow out of the holes?

I have not seen mention of this in any tutorials.
For the ground pad, in the past I have applied solder paste to the ground pad and leads. Then soldered the leads down to tie the chip in place, and then used a hot air gun - Actually a gas iron with hot air tip - and heated from the back until the solder flows in the vias.
You need to be gentle in heating things, and it will take a while. But this works.

Better still is to use a reflow oven. Now I have my "converted toaster oven" I use this to solder all ic's that have a ground pad.

To be honest though, if this is rework and there are other temperature sensitive parts such as plastic etc, I would consider the first approach.