Measure all your ingredients before beginning and have them ready. This is very important.
Prepare your baking pan by brushing the pan all over the inside and inner walls with canola oil. Line the pan with two sheets of parchment leaving overhangs. These will serve as slings for you to pull the caramels out of the pan later. You can use mini binder clips to fasten the parchment slings in place.
In a deep 3 quart saucepan, pour the water, and then the sugar. Don’t stir it.
Bring the mixture to a boil over medium heat. If there’s sugar stuck on the sides of the pan, carefully brush it with a heat-resistant silicone brush dipped in a little water. Feel free to swirl the pan to give the mixture a stir, but when you set it back on the burner, brush the edges of the pan with water to dissolve the sugar crystals from the walls of the pot.
Once the sugar is completely dissolved and the mixture starts to bubble, you can increase the heat on the stove to medium–high, or you can leave it on medium. The only difference is that on medium, it will take longer for the mixture to caramelize.
Continue to boil the caramel until it turns light amber in colour (don't let it get too dark!). As soon as the caramel has reached the desired colour, slide the pan off the heat, and turn the burner off.
Slowly and carefully drop in the cubed butter (it will bubble and erupt so be careful!). Pour in the cream, slowly and carefully.
When the bubbling has calmed down, begin to gently whisk the caramel until it is smooth and homogeneous.
Return the pan to the burner and turn it back on to medium–high. Bring the mixture back to the boil and cook the caramel until it reaches 121 ºC (250 ºF) on an instant read thermometer.
Once the caramel has reached the desired temperature, turn the burner off and carefully pour the hot caramel into the prepared pan.
Let the caramel set for 30 minutes, then sprinkle generously with flaky sea salt. Let the caramels set overnight.
When the caramels have set, remove the slab from the pan using the parchment sling to lift it out of the pan. Set it on a cutting board.
Brush a metal bench scraper with a little oil, then cut the slab of caramel into 49 pieces (so 7 rows x 7 columns). Individually wrap each caramel in a 4x4 inch square of parchment or wax paper, twisting the ends to secure the wrapper in place.