Partitioning a table with LOB columns in Oracle 11g
Yes, it seems you overlooked it indeed:

PARTITION BY HASH(X)
(PARTITION P1
    TABLESPACE T1
    LOB (my_lob_column) STORE AS (TABLESPACE T1_LOB  /* here */ ),
 PARTITION P2
    TABLESPACE ts2
    LOB (my_lob_column) STORE AS (TABLESPACE T2_LOB))
)