One day before bottling, defrost the wort you kept, boil it, chill it and pitch a highly flocculant yeast. If you don’t have a lager going at this time (like I usually have) use Wyeast 1056 or Nottingham Ale yeast. Let this start fermenting and gently add the fermenting starter w/o its sediment or Kraeusen to the bottling bucket. Add the beer and bottle.
(for 17L (4.5 gal) beer, you should need about 1.5 L (1.5 qt) Kraeusen for bottling. This assumes that the gravity of the Krauesen has not dropped below 9*P (1.040 SG) yet#
Keep the bottles at fermentation temp for about a week and the beer should be ready for drinking. Some age #2-4 weeks) will benefit it though.
See also Priming bottles with wort vs sugar.