### Relative Vector spaces

Consider a field L containing a subfield F. I would like to look at L as a F vector space without using the command relativise. Is there any way to obtain this.

For example :
Let L.=CyclotomicField(53*52), and F.**=CyclotomicField(53). **

** **I would like to construct a $F$ linear isomorphism $\phi : L \mapsto F^{24}$.