How to prevent 2yo rescue pup from getting separation anxiety

(Also posted in r/dogs)
Hello, hoping to get some advice about a 40 lb cattle dog (2yo female) I rescued approximately 7 days ago from a foster/shelter. For some background info, she was found as a stray in Texas and only spent about a month with a foster before being transferred to WA where I live. Before I adopted her, she was kenneled for a week at a grooming and doggy daycare that also partners as a foster rescue. As of today it has been 2 months since she left her stray life behind. I have had one other rescue dog (he passed in February) that came from an abusive home and it took a long time to rehabilitate him, but her training seems daunting and I question if I will be able to get through to her.

By all accounts she is a WONDERFUL dog. She is a “love bug” and loves to be pet and loves to cuddle. She is also a very sleepy dog but that could be the adjusting period so I can’t say much if it is truly her regular disposition. She needs a lot of obedience training but she is otherwise a very well behaved good dog that doesn’t make a sound (or so I thought), loves people and loves dogs. I do realize it is too early to tell how well she’ll settle since she’s still adjusting to her new life, but I’m a little concerned that she will start to develop separation anxiety. She is a very cuddly and submissive dog and has become very attached to me. I welcome her affection and don’t mind it at all as I am happy to know that she feels safe enough to show it. It has been a joy to help her adjust to being a dog that lives in a home and not in a rural desert. But will my constant attention to her affection and attention to her overall well-being cause her to become anxious when I leave her alone? Will it make training harder? Is it best to approach separation training by giving her less affectionate attention?

I’ve never crate trained a dog before, but her former foster said that she was crate trained; to what capacity I’m not sure. For example, I left her in her crate for 3 minutes to check the mail and she managed to squeeze out from under the crate door and escape. When I returned from the mailbox, she was anxiously waiting at the door. I reviewed the furbo footage and I was fairly shocked at how she escaped and am concerned that she will hurt herself in the future if this were to happen again. I would like to mention and am little ashamed to admit that before this crate incident, I did leave her alone to free roam around the apartment while I was called into work (My main job is work from home but I also have a gig-based part time job) and she lasted about 3 hours before she started scavenging around the house, bypassing the doggy gate to the kitchen and pulled out all the dishes from the sink, ate half a loaf of sourdough bread, and knocked down some random things on the kitchen counter. She barked for about an hour before I rushed home to asses the damage done which was just the half eaten loaf of bread (haha). My judgment was poor in leaving her alone so early into this adoption for such an extended period of time because she had been such a chill dog and would sleep away most of the day/night. But of course it’s different when someone is home vs not. I will be hiring a dog sitter on days I have to be at work but I do question if I need to take a different approach when giving her attention to reduce the possibility of developing full-blown separation anxiety. I am little shaken by the crate escape so I feel like I may be writing this in a panicked stupor but any experienced redditors out there willing to share their experience and/or advice would be helpful. Apologies for the long post.