Multiple passes with a quarter inch bit. Standard bit; won't be hard to find.

Are you wanting to route the end of the door? Do you have a router table?

Not seeing any slot cutting bits that will cut that deep. Max out at 3/8" depth.

Probably someone else will chime in with a better idea.

ci_lantro is correct. You need to do several passes. I would never try to hog out to a 3/4" depth in one pass. If you are looking for a reasonably priced site where you can buy quality bits, try: MLCS

Ok good to know. May just have HD do the install. Thanks all!

I was looking at this. Do you think 3 passes with this guy will do the trick? My father in law luckily has a router table I can use. I also have a Bosch plunge router.

https://www.amazon.com/Yonico-14911q-4-Inch-Bearing-Cutter/dp/B078HRRKMS

aspiringdiyer- The router bit in the link will definitely not work as it cuts exactly 1/4" deep...no more, no less. A further problem is that a router table will not be useful as there is no practical way to stabilize a door and move it across the table: it will either be impossible or you'll mess up the door when the door wobbles and slips. To do this correctly you need two things: 1) a basic, straight 1/4" diameter bit that you can progressively lower into the workpiece until you have routed out to a 3/4" depth, and 2) an edge guide attached to the router so you keep the router bit in the correct location as you move the router along the door edge...like one of these:

If you are unaware of how to do this properly, you should enlist the help of a woodworking friend.

Great! Thanks Kudzu

aspiringdiyer- You're welcome. Presumably what I wrote makes sense, but, if you have further questions, ask.

And I hope you didn't think I was insulting your DIY skills: I just didn't want you to get hurt and/or mess up an expensive door.

Oh no worries! I really appreciate your insight