Wintering Japanese Yew Zone 7a

[Japark]

Dear Fellow Bonsains!
May I ask your help in wintering my bonsai? Below is the situation I’m working with:

• Zone 7a
• Japanese Yew
• ~14” tall
• ~14 years old
• 1st winter with me
• In plastic pot
• Must be wintered outdoors in open field (no option to bring indoors)
• No electricity
• Have access to mulch
• No local bonsai club (@ least that I can communicate with
• Can build something simple if needed to

After reading the other posts I realize the idea is to keep it consistently cold, and I realize that my trees roots probably can’t handle my zone. I was thinking about digging a hole in the ground, mulching that, then putting mulch all around the pot. Someone even suggested covering the whole plant in mulch? Getting confused.
Questions:
If I do either of the options above, should I water it?
Any other options?
Thanks for your advice, experience, and time friends!