Your window is nearly over if the bark is still slipping now. I have never tried them this late but I have done them in late June in prior years to the tune of about 50/50 percent success or lower. Really it’s a spring to middle of June Graft where greenwood budding takes over and then bud grafts. But, ‘The Mega Chip’ can be used at all times of the season. I did a demo on that too.
One more comment and that is flap-grafting may certainly be done anytime the bark is slipping properly but the later you go the less takes.
Here’s that demonstration of the Mega Chip that Tom Wahl at Red Fern Farm showed to me last year:
Dax