I've talked on here about my Pixel 4a and how much I like it, but the battery life has been really dreadful as of late. I was at 900+ cycles on the stock battery so not exactly a surprise, but I didn't want to buy a new phone so replacing the battery seemed the best way forward. I got a kit from iFixit for ~$60 including an OEM battery.
I read online that it's a tough process since the 4a has a very fragile screen that's likely to break during such repairs, but everything went (mostly) fine! The iFixit guide got me most of the way there but I supplemented with a YouTube video. Hardest part was actually removing the adhesive strips keeping the battery in place, I ended up having to use isopropyl alcohol to dissolve some of the glue instead of pulling it out. Also I did kinda puncture the old battery which shot out some sparks, but it seems to be stable (currently chilling on my kitchen table until I can take it to be recycled/disposed of properly).
One thing to note about the iFixit kit is that the included adhesive strips for sticking the screen back on are kinda doodoo and likely to get stuck on the kit packaging during transit, which ruins them. I tried to make do with the remaining strips but noticed edges of the screen sticking up, so I replaced it the next day using some TESA tape I got off Amazon which seems to work great.
Overall kinda sucks that you have to jump through so many hoops, but was also somewhat satisfying to feel like I accomished something. And of course battery life is much better!
The bucket of sand is a good tip, my solution was an empty paint can filled with sand and the lid hammered back on.