The material looks like fabric, in other words, the 'canvas' (actually linen) used to 'skin' earlier aircraft. If this is the case, then it's possible that this piece is from a Wellington, rather than a Lancaster, the latter being all metal construction and 'skin'.
The space between the taped seams might give more of a clue, as no dimensions are given, but that would still not postively identify if it is from a Wellington, or any other aircraft, or even if it's genuine.
It does have 'the look' of being a section of aircraft covering, but 'cut from' a crashed aircraft is slightly dubious - this, in normal circumstances, would be a chargeable offence, unless it was to preserve the art work for whatver reason.