For crust, in large bowl, combine oats, flour, sugar, and salt; then stir in melted coconut oil to incorporate. The mixture should hold together when squished between your hands. Spelt flour tends to vary in absorbency, so water may be needed to bind crust; if this is the case, add water, 1 Tbsp at a time, until crust holds together tightly. Press crust firmly into prepared pan and bake for 20 to 30 minutes, until crust is dry to the touch and beginning to brown around edges. Remove from oven and cool completely in pan. If you intend to transport tart, leave cooled crust in pan for assembly and serving. Alternatively, using parchment paper, remove crust from pan and place on rectangular serving plate.