Advice for a newbie - on-line Christmas Waitrose shopping

[ItsMyIssue]

Never had a Christmas food shop delivery before. I’ve added my Christmas wine to book the slot. I don’t need a turkey, just party food, Christmas lunch veg/sides etc…. Do I need to do load my basket with everything I want now and then just amend the day before delivery or just do it all the day before?

I usually do the same, reserve the slot with wine then amend
You can do it just before but you stand a better chance of getting the items you want if you do it earlier.
My delivery is 21st and I’ve just added all the items I want

yes load basket with what you want now and check it out

if you do that and don't amend it, they will substitute any missing items very generously

take care though as some "Entertaining" range items can't be canceled or can't be canceled after a specific date eg 15th Dec

I think you have to have finalised your basket by midday the day before, so check that. Other supermarkets it’s usually around 11pm the day before.