Important to prep your materials and ingredients as this is a heat sensitive and may be hazardous moving heated up things around etc.so prep your all your utensils that will fit together.

Start caramelisation about half water amount to sugar warm up on med high heat without stiring, but swirl pan around gently only at freq intervals InshaAllah not to stick.or burn.and to combine evenly

Once the sugar is bubbling, and enof caramelisation has taken place to coat the tin without being runny,otherwise it will not solidify.so to do this gently pour the thick caramelized sugar into the remkins while moving it around gently to coat all edges.work fast as to allow even cooling and evenly coat,before cooling

Beat the eggs in a separate bowl until well beaten then set aside for step 5 inshaAllah.can add pinch of salt to egg

Use the same pan of caramel,to briefly warm milk up.NOT boil it!then add the vanilla.

To the beaten egg add your slightly cooled(NOT hot) milk.fill the remkins about two third or three forths way up,to avoid spilling while moving & during cooking etc

Add boiling hot water in a tray,about half way the depth of dishes/remkins you aur using to bake,Place the custard/flan mixture and then cover the tray so that no water can entre the tray while steaming

Preheat oven if necessary.otherwise if water bath may be suffucient to start the baking process,so bake in carefully handling the water bath with dishes in side.then now bake about 15 mins on medium high.check if it is cooking by either a picking stick or the wobble test

Then about approx 15 mins only required to form the flan so can check if done if not just giv it more time.it may form bubbles at base and at surface may or may change color at end depending on initial colour of the mixture it may remain pale etc.try not to over cook you can tell this if texture becomes tougher and taste is greatly compromised too.and not nutritious to over cook food as you may well know!
Alhamdulillah you done it...Bismillah and enjoy