This little mosaic is easiest tutorial I could think of for the absolute beginner to mosaics - Using only pre-cut tiles in a small but practical coaster.
Supplies are all from good old Amazon:
Purple Tiles: https://amzn.to/3gmcZYG
Green Dots: https://amzn.to/2DqyJnM
Grout: https://amzn.to/3fk6Zi1
Wooden blanks: https://amzn.to/3fgavtz