Read Option slot/slant blocking on the spy or outside LB'er to open the secondary.
Matthews IMHO has been excellent on blocking down the DE to allow off tackle option pulls and runs.
The slot on running plays, specifically on read option, has a heavy blocking burden for the "option" part to even be viable.
Depending on who the TE is blocking, the lead RB is blocking (if there is one), etc. the slot receiver may have a simple task of blocking his cover defender (FS or Nickel) or crashing down on the LBer, etc.
Jeurgens from what I have seen seems to be solid with his blocking assignments.