Assembly is done using the provided Assembler:

public void assemble( ModuleAssembly module )
{
  [...snip...]

    new EhCacheAssembler()
        .withConfig( confModule, Visibility.layer )
        .assemble( module );
}

Here are the configuration properties for the EhCache EntityStore Cache:

public interface EhCacheConfiguration {

    /**
     * Heap tier size.
     *
     * Default to 1MB, you may want to change this.
     *
     * @return Heap tier size
     */
    @UseDefaults( "1" )
    Property<Long> heapSize();

    /**
     * Heap tier size unit.
     *
     * @return Heap tier size unit
     */
    @OneOf( { "B", "KB", "MB", "GB", "TB", "PB" } )
    @UseDefaults( "MB" )
    Property<String> heapUnit();

    /**
     * Optional off-heap tier size.
     *
     * @return Optional off-heap tier size
     */
    @Optional
    Property<Long> offHeapSize();

    /**
     * Off-heap tier size unit.
     *
     * @return Off-heap tier size unit
     */
    @OneOf( { "B", "KB", "MB", "GB", "TB", "PB" } )
    @UseDefaults( "MB" )
    Property<String> offHeapUnit();

    /**
     * Optional disk tier size.
     *
     * @return Optional disk tier size
     */
    @Optional
    Property<Long> diskSize();

    /**
     * Disk tier size unit.
     *
     * @return Disk tier size unit
     */
    @OneOf( { "B", "KB", "MB", "GB", "TB", "PB" } )
    @UseDefaults( "MB" )
    Property<String> diskUnit();

    /**
     * If the disk tier is persistent or not.
     *
     * @return If the disk tier is persistent or not
     */
    @UseDefaults
    Property<Boolean> diskPersistent();

    /**
     * Maximum size of cached objects.
     *
     * @return Maximum size of cached objects
     */
    @Optional
    Property<Long> maxObjectSize();

    /**
     * Unit for maximum size of cached objects.
     *
     * @return Unit for maximum size of cached objects
     */
    @OneOf( { "B", "KB", "MB", "GB", "TB", "PB" } )
    @UseDefaults( "MB" )
    Property<String> maxObjectSizeUnit();

    /**
     * Maximum cached object graph depth.
     *
     * @return Maximum cached object graph depth
     */
    @Optional
    Property<Long> maxObjectGraphDepth();

    /**
     * Expiry policy.
     *
     * @return Expiry policy
     */
    @OneOf( { "NONE", "TIME_TO_IDLE", "TIME_TO_LIVE" } )
    @UseDefaults( "NONE" )
    Property<String> expiry();

    /**
     * Expiry length.
     *
     * @return Expiry length
     */
    @Optional
    Property<Long> expiryLength();

    /**
     * Expiry time unit.
     *
     * @return Expiry time unit
     */
    @OneOf( { "MILLISECONDS", "SECONDS", "MINUTES", "HOURS", "DAYS" } )
    @UseDefaults( "SECONDS" )
    Property<String> expiryTimeUnit();
}

Cache overflow to disk may be configured using the FileConfig Library. If the FileConfig library is not in use, then it defaults to a temporary directory in java.io.tmpdir.