Preheat the oven to 350°F. Spray a 13 by 9-inch baking pan with nonstick cooking spray and line with parchment paper, leaving a 2-inch overhang. Spray the parchment paper with nonstick cooking spray.
Stir together the rolled oats, flour, brown sugar, baking soda, cinnamon, and salt in a large bowl. Add the butter and boiled water and stir until well combined. Press two-thirds of the mixture in an even layer over the bottom of the prepared baking pan. Bake for 10 to 12 minutes, until golden brown. Remove from the oven and let cool completely.
Stir together the brown sugar, flour, lemon zest, and cinnamon in a medium bowl. Add the strawberries and lemon juice and toss to combine. Spoon the filling over the cooled crust and sprinkle the remaining crumb mixture over the fruit. Bake for 30 to 35 minutes, until the top is golden brown and the fruit is tender. Remove from the oven and let cool completely. Cut into squares and serve.