Here’s another variation on the slapback theme. Just a touch of movement for doubling, with a slow RATE, low DEPTH L-C-R (more at center), a little DETUNE MIX, at a 5C DETUNE spread; all anchored at DELAY 15.0 mS.
The expression pedal is what fades into the 100 mS DELAY here [no ENV MIX active]. Increasing DETUNE MIX blurs & fattens the entrance. Your dry signal is mixed back as the echo becomes more prominent. The crossfade between DELAY values adds to all the movement, & creates some unusual doubling FX.