Lightly coat a 13-by-9-inch rimmed baking sheet with oil. Line with parchment, allowing 2 inches to hang over the long sides. Bring sugar and water to a boil in a small saucepan over medium-high heat, tilting pan to swirl and washing down sides with a wet pastry brush to prevent crystals from forming. Boil, without stirring, until mixture turns medium amber, 10 to 12 minutes.
Remove from heat, and stir in pistachios and salt. Pour mixture onto prepared baking sheet, and quickly spread evenly with an offset spatula. Let cool until just set but still soft, about 2 minutes. Using the parchment as handles, transfer warm praline to a cutting board. Immediately cut praline into bars of desired size using a serrated knife lightly coated with oil. Let cool completely. Bars can be stored in an airtight container at room temperature for up to 2 weeks.