I need to resample a 30m DEM to a 100m slope raster. Do I just resample the 30m DEM directly to the 100m slope raster? or, do I convert the 30m DEM to a 100m DEM and then create a 100m slope raster from the new 100m DEM file?
It would be best to resample the DEM and then create the slope layer.
Take a look at this thread (particularly post 2) from the ESRI forums.
You might end up saving yourself some time this way as well. Resampling a DEM will reduce it's size (in terms of disk space), and should allow the slope tool to process in a shorter amount of time.