How do I setup a CloudFlare Origin Certificate in AWS Certificate Manager?

CloudFlare published the key chain certificates in their support article here: https://support.cloudflare.com/hc/en-us/articles/218689638-What-are-the-root-certificate-authorities-CAs-used-with-Cloudflare-Origin-CA-

Which Origin CA you use, depends on if you used their RCA or ECDSA cert creation. If you aren't sure which you used, run this command on the public cert, openssl x509 -in cert.crt -text -noout|grep "Signature Algorithm"

Cloudflare Origin CA — RSA Root

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

Cloudflare Origin CA — ECC Root

-----BEGIN CERTIFICATE-----
MIICiDCCAi6gAwIBAgIUXZP3MWb8MKwBE1Qbawsp1sfA/Y4wCgYIKoZIzj0EAwIw
gY8xCzAJBgNVBAYTAlVTMRMwEQYDVQQIEwpDYWxpZm9ybmlhMRYwFAYDVQQHEw1T
YW4gRnJhbmNpc2NvMRkwFwYDVQQKExBDbG91ZEZsYXJlLCBJbmMuMTgwNgYDVQQL
Ey9DbG91ZEZsYXJlIE9yaWdpbiBTU0wgRUNDIENlcnRpZmljYXRlIEF1dGhvcml0
eTAeFw0xNjAyMjIxODI0MDBaFw0yMTAyMjIwMDI0MDBaMIGPMQswCQYDVQQGEwJV
UzETMBEGA1UECBMKQ2FsaWZvcm5pYTEWMBQGA1UEBxMNU2FuIEZyYW5jaXNjbzEZ
MBcGA1UEChMQQ2xvdWRGbGFyZSwgSW5jLjE4MDYGA1UECxMvQ2xvdWRGbGFyZSBP
cmlnaW4gU1NMIEVDQyBDZXJ0aWZpY2F0ZSBBdXRob3JpdHkwWTATBgcqhkjOPQIB
BggqhkjOPQMBBwNCAASR+sGALuaGshnUbcxKry+0LEXZ4NY6JUAtSeA6g87K3jaA
xpIg9G50PokpfWkhbarLfpcZu0UAoYy2su0EhN7wo2YwZDAOBgNVHQ8BAf8EBAMC
AQYwEgYDVR0TAQH/BAgwBgEB/wIBAjAdBgNVHQ4EFgQUhTBdOypw1O3VkmcH/es5
tBoOOKcwHwYDVR0jBBgwFoAUhTBdOypw1O3VkmcH/es5tBoOOKcwCgYIKoZIzj0E
AwIDSAAwRQIgEiIEHQr5UKma50D1WRMJBUSgjg24U8n8E2mfw/8UPz0CIQCr5V/e
mcifak4CQsr+DH4pn5SJD7JxtCG3YGswW8QZsw==
-----END CERTIFICATE-----

Finally resolved the issue by just trial and error:

Get root CA from: https://support.cloudflare.com/hc/en-us/articles/218689638-What-are-the-root-certificate-authorities-CAs-used-with-Cloudflare-Origin-CA-

For example, in RSA format:

-----BEGIN CERTIFICATE-----
Cloudflare Origin CA 
-----END CERTIFICATE-----

And you have your own Certificate as:

-----BEGIN CERTIFICATE-----
Your own
-----END CERTIFICATE-----

Now, you put them in to AWS certificate management console as the following:

Certificate

-----BEGIN CERTIFICATE-----
Your own
-----END CERTIFICATE-----

Secret

your secret

Certificate Chain, you need to combine your own certificate and cloudflare root CA, and notice the sequence matters!

-----BEGIN CERTIFICATE-----
Cloudflare Origin CA 
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
Your own
-----END CERTIFICATE-----