Hi guys,
I'm new to the Avios program and looking for some help as to how it works.
I have some Chase Ultimate Rewards points that I'm looking to transfer over to EI to book a BOS - DUB or SNN return trip.

My questions are:

• Do I need to look up award availability firstly on Avios.com and then book on EI website or Avios website? FWIW - The Avios website seems really bad and slow. I have tried multiple browsers and it just seems really clunky.
• Does there need to be reward availability firstly or can I simply book on EI website, and use Avios for the form of payment as per their Avios chart amounts?

I guess what Im asking is say I want to travel on particular days in June. Before I transfer over the chase points to Avios, does there need to be points redemption flights for the dates I want to travel or will the EI website always let me pay in Avios points as per their chart amounts (when it come to the payment stage)?

Thanks for any help!