Dual battery ideas non underhood?

I’ve read through a lot of dual battery posts and threads but I haven’t seen may posts or pictures of places people have mounted them other than under the hood. I just don’t have the space under my hood anywhere bc I’ve either installed fuse block or the brake system is on the passenger side fender well. I also have no room behind the back seats as I’ve installed an audio system that uses that space.

Does anybody have any pics of theirs in the bed using the storage compartments? I’ve got a redarc bcdc charger that I need to mount beside my secondary battery also and I’ve started and stopped several times after hoping to figure better ideas. I don’t want to use my bed space being my truck is a 2017 TRD Sport DCSB. Thanks for any ideas and especially pictures of what you’ve come up with to help me use your creativity and make something safe and efficient