Line an 8-inch square pan with a piece of parchment paper. Mix the oat flour, protein powder, rice crisp, and salt together in a large bowl.Add in the nut/seed butter, maple syrup, and vanilla. Stir well to combine. If the mixture is a bit dry, add a splash of non-dairy milk and mix again.Press into pan and roll out with a pastry roller until smooth. Pop into the freezer.Melt the chocolate chips and coconut oil together in a small pot over low heat. When half of the chips have melted, remove from heat and stir until smooth.After freezing the bars for about 5-10 minutes, remove from freezer and slice into bars. Drizzle with melted chocolate and freeze again until set. Store in the freezer for a week or longer in an air-tight freezer bag or container.