I am new to forum. How do I add filling to a sheet cake? Do I level the cake and then take a cake board to remove the top layer? Then do I carefully put the layer back on?
You got it!!
Yep, but I wouldn't waste a cake board to move it! Once you've cut the torte line, slide a large cookie sheet in there to remove the top.
If you aren't comfortable splitting and lifting a sheet cake then you could also bake the cake twice. Use half the batter and bake two short layers, then just trim any hump in the center and fill. This way you can park the top layer in the freezer while you fill the bottom. Then it will be firmed up and easier to move around without cracking.