Skirting outside corners - how to fill big gap

[marmage]

Will need a deep mitre box , you could just cut square joints and caulk .

Thanks so much, yes it's a deep enough one for the 70mm skirting we got. If that fails I'll move on to square joints!

Thank you everyone!

 

[marmage]

Having failed the mitre joins with a plastic mitre box, we decided to do the square joints. Please may I ask what is the best product to fill the gaps where the two corners of the skirting join? Assuming will paint over white. The skirting is a simple MDF rectangle profile and came primed white.

Many thanks!

 

[marmage]

To add, the skirting profile is a simple rectangle profile. I know it's not ideal but we just couldn't get a good cut with the mitre!