audio – FFMPEG: Combine mono-wav files into multi-channel wav

Our recording device records each input on a seperate wav file, instead of one multi channel one.
I’d like to clean this up a bit, so I don’t have to deal with 4-8 files/shot.

I tried multiple commands so far, but they all either produce just a 1 channel file, or a corrupt one.

Commands I tried:

ffmpeg -i 1.wav -i 2.wav -filter_complex "[0:a:0][1:a:0]amerge=inputs=2" output.wav
ffmpeg -i file1.wav -i file2.wav -i file3.wav -filter_complex "[0:a][1:a][2:a]amerge=inputs=3[a]" -map "[a]" -ac 3 output.wav

I also tried to follow the documentation: ffmpeg.org/ffmpeg-filters.html#toc-channelmap

Any ideas what I am missing/how I could do this?