I think the best thing to do... is stop using the phone as much as possible. Try to minimize "needing" to use the phone in the car. Then leave it somewhere attached, or practically attached, to you. Like a pocket, phone holster/clip or purse... assuming you never forget the purse.
For myself, I have a Samsung Zflip3. I bought that because it can fold into such a small form to fit in my pocket. Let me admit ahead of time, I have forgotten my phone in the car a handful of times (could probably actually count the times with the fingers on one hand). That said, because I usually leave my phone in my pocket, I have to struggle and go out of my way to pull my phone out to use it in the car. And if I don't pull it out of my pocket, then there's no way I can forget it.
I don't use my phone for music, that's on a USB drive.
I don't use waze or any other navigation on the phone, the car's navigation is more than enough for me.
With Bluetooth, I can make/receive phone calls and pass messaging through the car. Though messaging is a bit awkward. Still working on it.
I don't surf the web or do any other media (for times when you're sitting around waiting for something) on my phone, that's what my iPad is for. As big as the biggest phones out there (even the zFold series), I find an iPad is just plan easier on my eyes. While my iPad does have the Tesla app installed, I didn't enable phone key on it. So, even if I leave the iPad, it won't make a difference when it comes to accessing/driving the Tesla.
I do use my phone to order food (usually when at a stop light), while I'm on my way there. In-between stop lights or once I'm done, I keep it in my hand BECAUSE I don't have a mount for it. Yes, I steer with one hand... consider my other car is a stick shift, it ain't that different. Because I'm usually already at work (I do deliveries), I try as much as possible to order while I'm in-between deliveries and not in the car. After that meal at the beginning of my shift, I no longer need to pull out my phone for the rest of the evening of deliveries.