Using two electrolysis will give us Ag/AgCl electrode:
1) in AgNO3 + HNO3 solusion (base electrode will be cathode of electrolysis.Anode can be Pt Or Ag
2) in HCl solution (Ag coated base electrode will be Anode. Cathode will be a Pt electrode.
Try to find best conditions of electrolysis (concentration and current density and voltage)