To make a playlist with Alexa on your Echo device, you have the option to ask Alexa or create one using the Music app.
How to Make a Playlist on Alexa Using Music or Your Echo
How to Create a Playlist With Music
Alexa Multi-Room Audio - Music and Entertainment
How to Customize Music With Alexa
Simple Ways to Create Music Playlist
How to Create a Playlist on Echo Show
How to create and edit music playlists with Alexa
How to create and edit an Echo playlist - Android Authority
Converse naturally with Alexa to pinpoint the perfect playlist on Music.
How to play music with Alexa? - The Spotify Community