Just about every recent flagship phone is a nightmare to repair, from the Galaxy S10 to the Huawei P20 Pro. As it turns out, building phones out of unibody glass with lots of glue and solder doesn't make it easy to replace the battery. However, the Pixel 3a and 3a XL appear to be a nice change from pace, as iFixit's new teardown guides claim both phones aren't too daunting to fix.
iFixit tore down both phones, but only the 3a has a detailed text guide — the 3a XL just has a video. Unlike some previous generations of Pixels, both devices were manufactured by Google (using former HTC engineers), so the internal layout and repair steps are very similar. Popping open the device doesn't require any heat.
Quite good news and I imagine it is also partly due to the phones not being waterproof. Personally, I'd got for repairability (esp battery and screen) over waterproof ability. I had to buy a heat gun and toolkit to open my Nexus 6P to replace the battery.