Flushing one plant apart from the others?

I 4 plants in an RDWC container, 3 are of one strain, 1 from another. The lone strain is finishing up and I'd like to send it to flush. I thought about putting a separate container in the main bucket and let it flush apart from the others.
I saw somewhere, where you could chop the stem and set it in water but that doesn't seem right.

Any suggestions?

definitely dont cut it and stick it in water. id say get a separate container set up for standard dwc and flush it in that. make sure that the rdwc site that is left vacant is sufficiently protected from light penetration and whatnot.

I figured there's no real solution to this, the others were closer than I thought so I just went ahead and started flushing them all. Thanks for the reply!