If your fMRI results (using FSL) are in MNI space, you can use the following Freesurfer command to get beautiful figures for presenting your results.
For right hemisphere:
tksurfer fsaverage rh inflated -overlay <thresh_zstat_imagename>
For left hemisphere:
tksurfer fsaverage lh inflated -overlay <thresh_zstat_imagename>
This is an approximation and only for display purposes, but it works (without registration) since the fsaverage brain is in MNI space as well.