Try this.
labroot@jtac- # run request system snapshot slice alternate
Doing the initial labeling...
Verifying compatibility of destination media partitions...
Running newfs (886MB) on internal media / partition (da0s2a)...
Running newfs (93MB) on internal media /config partition (da0s2e)...
Copying '/dev/da0s1a' to '/dev/da0s2a' .. (this may take a few minutes)