One pattern suffice.
Ex with 2 bars looping (4 bars with 1/2 scale, increase RLEN to 64)
Pattern length = 64
Track 1 :
Flex Recording 1, trig on step 1
Recording 2 on step 32 (sample lock, trig + level to set it)
Recorder 1
RLEN = 32, rec trig step 32, SRC3=CUE
Recorder 2
RLEN = 32, rec trig step 1, SRC3=CUE
Activate CUE (CUE + TRACK or Studio mode)
(For an even more stable volume I added +20/127 on VOL with lfo designer designed with 1 max, depth 20, but it works without, loosing level slowly).