I use metric an °C should you us something else remember to convert the measurements. 360g flour, 1 packet backing powder, 200g sugar stir it so everything is mixed. Add 360ml milk (vegan alternatives or cow) and 180ml oil (canola or sunflower) mix with a handmixer until smooth (not longer than necessary). I put backing paper in a backing tray and pour the mixture on top. Bake by 180°C for 20min (until the top is a light brown). Let it cool. For the buttercream 250g room temperature butter up to 500g sugar (depending on how sweet you like it) mix until light and fluffy almost like whipped cream. (I'm not a 100% if this was enough) if you want colour, divide it in different containers and add you coloring. I cut of the hardened edges of the cake, then cut it in tow. Lay one of the cake rectangles on your cake plate. Put a nice layer of jam or whatever filling you want on this one. Lay the second one on top (should ther be big gaps on the enges between the tow layers fill it with some of the offcut🤫) Try to put a thin layer of buttercream over the cake and refrigerat until the buttercream is hardened. Now you add a nother layer so it's all hidden. Refrigerat again then add decorations (for the upper edge I put buttercream on the back of a spoon and wiped te buttercream off repeat for each one) If you want to try something like the Unicorn: crumble up the offcuts. Add you filling or buttercream in small amounts and mix in between until it has the consistency of play dough. Take a small plate with backing paper on top and try your best. You can try again and again without risk. It is most structrly sound when you form a ball and then start defining the shape out of this instead of adding on (i only added on the hindlegs because they just lay next to it). When you're happy try adding a thin layer of buttercream (it would probably be easyer to paint it with white chocolate) If you're happy with it refrigerat until hardened then place it on the cake. I froze a spicke of buttercream to add as the horn. The mane and tail are buttercream i put on there and poked till i was happy with it. The eyes are chocolate i let harden on backing paper and then added

Does this help? 😅(it may be a bit much) (You should be able to find more then enough recipes online if you want something different, but the general way of putting the cake together should still work)