Heat oven to 425°F (175°C).
Grease and flour a 12-cup muffin tin or line with paper liners. (If lining with paper liners, spray each liner well with cooking spray).
Combine flour, granulated sugar, baking powder and salt in a small bowl; set aside.
In another bowl, whisk avocado oil, half-and-half, eggs, almond extract, poppy seeds and sliced almonds until smooth.
Add dry ingredients mixing just until moistened.
Fill prepared muffin tins almost full.
Bake muffins at 425° for 5 minutes.
Reduce heat to 350° and bake for an additional 13 to 15 minutes, or until muffins test done when a toothpick inserted in center comes out clean.
Cool in pan on wire rack.
Add glaze and allow icing to dry about 15 minutes before serving.
Makes 1 dozen muffins.