how to flash recovery img ?

Hello, on any custom roms we see recovery as img, so whats the ultimate good process to actually flash it?
img to tar bootloop
any other recovery bootloop
only one thats working is "twrp-z3s-3.5.0_10-A11_6+vbmeta_DUB5" BUT i have x1s, so pain to flash some rom.

Im currently on beyond rom 3.1, because i cant flash anything else.

Any help here?