Creating the most basic Scala project with Maven?

You should be able to use mvn archetype:generate. You can choose, e.g., org.scala-tools.archetypes:scala-archetype-simple. You need to put in the number number next to the archetype name in the output of your mvn archetype:generate command because the numbering can change over time. There are also other options like eu.stratosphere:quickstart-scala as documented in this article.

They may be somewhat outdated, though. I personally prefer writing my pom.xml files manually. For reference, here is a minimal pom file for use with Scala 2.11.6 and Scalatest 2.2.5:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>my-artifact</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <encoding>UTF-8</encoding>
    <scala.version>2.11.6</scala.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.scala-lang</groupId>
      <artifactId>scala-library</artifactId>
      <version>${scala.version}</version>
    </dependency>

    <dependency>
      <groupId>org.scalatest</groupId>
      <artifactId>scalatest_2.11</artifactId>
      <version>2.2.5</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.scala-tools</groupId>
        <artifactId>maven-scala-plugin</artifactId>
        <version>2.15.2</version>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>
              <goal>testCompile</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

      <plugin>
        <groupId>org.scalatest</groupId>
        <artifactId>scalatest-maven-plugin</artifactId>
        <version>1.0</version>
        <configuration>
        </configuration>
        <executions>
          <execution>
            <id>test</id>
            <goals>
              <goal>test</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

    </plugins>

  </build>
</project>