Mistress and man were engaged in the operation of making a lamb "take," which is performed whenever an ewe has lost her own offspring, one of the twins of another ewe being given her as a substitute. Gabriel had skinned the dead lamb, and was tying the skin over the body of the live lamb,
Oh boy. Disguise? Masquerading as lovers? Has Bathsheba taken the place of another potential love of Boldwood's life, such as Fanny Robin, who is lost to him? Or is this just a metaphor for the early stages of love, when we are likely to cloak ourselves or seem outwardly appealing/palatable to earn a lover's interest/affections
