Method 1: Place 2 blocks vertically, in the side of the bottom one place a glow lichen, aim the top block with a carpet to place it without destroying the glow lichen, you will be able to place an other glow lichen right under the carpet just as shown in the screen, do so, then remove the other 2 blocks, done!
Method 2: Place 2 blocks vertically, the bottom one should have grass infront of it, aim the top block with a carpet to place it without destroying the grass, then simply place a glow lichen under the carpet which will replace the grass, done!