Job description. Feedback. Meetings to strategize.

take them to training, team building, and conference to give them time to be enlighted on new things in career and to relax away from work

Remove the assumptions. Are they "making excuses" or are they prioritizing their tasks? Are they "making excuses" or are your expectations not aligned... with reality? Are they making excuses or are they telling you why they do not believe the task is appropriate or that they cannot prioritize it? How are they "very good at what they do" if they are constantly making excuses to not do things? Whenever you identify an "issue" (whether interpersonally, professionally, physically, etc), you cant really fix it without understanding it. People can tell you what to do to motivate them, but if the problem is that they literally do not have time to do it, motivation isnt going to change that.
A lot of "managers" do not respect the actual time and effort people put into work and underestimate the amount of time a task takes to complete. Sometimes employees make "excuses" because they are more likely to be respected than just saying "i dont have time for that." more

A nonchalant customer isn’t necessarily rude—they’re just indifferent, distracted, or not fully convinced yet. The worst thing you can do is match... their energy or push too hard. The goal is to stay calm, guide the conversation, and gently pull them in. more

Remember that these actions will cost you money.

Assign external auditor on them half annually.
This is not necessarily to check them for any flaws but just to keep them to the heat.

Also, you may... engage the services of intelligents graduate interns and or attachments. Assign them to these nonchalant employees to account or report on them weekly.

Trust me, some of these interns can introduce stiff competition within the staff. Intentionally, religate some of their duties to these intelligent graduate interns .
On the days when they are unable to report to work for whatever reason, ask them to hand over to their keys to their interns.

They would sit up!  more

I suggest that to cope with non-chalant staffs, I would be motivating by some quote and over some training to them that will encourage them.

First off let me say that non-chalants is very subjective. That said lets deal with the issue as you have suggested it exists. There may be two issues... playing out here. One may be that your staff are unmotivated to do the job. This is a management issue and needs to be resolved at this level. Staff may not feel invested in their work or may feel undervalued. Secondly, if these staff are very good at what they do, they may just be plain bored and unstimulated by their current work. Highly competent people need highly stimulating work, or they will appear disinterested and complacent. If these people are not involved in stimulating work that challenges their skill sets, they will eventually underperform or leave for more exciting roles. It might be time to evaluate the type of work they are being tasked to do and determine if this is meeting their stimulation levels. If it's not, they are bored out of their minds and require significantly more stimulating work.  more

Set specific deadlines and follow up.
Address it privately eg You’re very skilled, but delays and excuses are affecting the team.

Honestly it looks frustrating sometimes, when you as the head is having focus and planned strategies to meet up with the effort demanded to complete... the task at a set time but your colleague that supposed to be your confidant becomes antagonist drawing you back to a tight corner. In such cases, I usually take authority as the head of the unit to assign duties through memos and copy the management, so failure to comply lead to neglect of duty which is a serious offense. I approach all staff with love avoiding issue of queries but use diplomacy to get on with all the staff. more

It is incredibly draining to manage high-performers who lack the drive to actually execute. However, as leaders, our primary job isn't just to assign... tasks; it’s to inspire. If a skilled employee is complacent, they might be bored or disconnected from the 'why' behind the work. They know how to do it, but they’ve lost the reason why it matters. more

Check behind the excuses and see what really are their complacency about, then work around the complacency issues as well as seeking ways of... motivating them. more

Giving them reorientation!

If they are under your leadership, I would suggest some type of motivation or training to teach them how to not be complacent or make excuses. If... they are very good at what they do and have the required skills, you can also make sure they have the resources necessary to weed out excuses and complacency. Rewards for a job well done are always in order.  more