I loved my fabric phone cover but it did look tatty so I gave in and bought another (only a cheapo one though as I am going to craft that too) while I played with my old favourite.

so simple:

fabric larger than the cover when unfolded

mod podge , classic not even fabric one

sharp scissors and a biro

Unfold the cover and lay it as flat as possible over the wrong side of he fabric then trace around the edge and mark through the holes (3 on the iphone)

remove the leather trim or embellishment from the old cover so there is a flat surface

cut out the fabric leaving a generous border for now and trim out the lens hole etc fairly neatly but under rather than over cut

coat the old cover with a layer of mod podge then smooth the new fabric in place. Start by positioning the lens holes and the rest can be stroked in place. Add a couple more coats of mod podge -letting it dry between coats. When the fabric feels papery trim the edges more precisely and neaten up the lens holes by rubbing the point of a crochet hook or similar inside them

fold and unfold the cover a couple of times to check the fabric gives and maybe let the glue cure a day or so before you use it

i will let you know how durable this is, but have plenty of scraps to do a refit next time